mosquito bites

How to get rid of mosquito bites

Mosquitoes are insects that live all over the world. There are thousands of different species of mosquitoes; about 200 of those live in the United States. The best treatment for mosquito bites is to avoid scratching the bites, as scratching further aggravates the inflammation and actually makes the itching worse. There are a lot of “home remedy” treatments for mosquito bites, not all of which work for everybody. Some people swear by the “soap remedy,” which is simply rubbing a dry bar of soap on the bite. Others reach for an alcohol swab, honey, vinegar, or a paste made from baking soda and water. However, doctors found that a layer of cool compresses placed directly over the bites tends to soothe the skin and lessen the itch.

Not all mosquito bites are equal because there are many species of mosquito, and you may react differently to each. If discomfort from a bite or the itch-scratch cycle becomes a problem, you may consider using a mild topical steroid such as cortisone cream or oral antihistamines. Doctors advice avoiding topical Benadryl® compounds and Neosporin® because they can cause contact dermatitis in those who have sensitive skin, resulting in a condition worse than the bites.

Instead, stick to soothing, nonirritating lotions like calamine or Sarna® Anti-Itch Lotion, both effective and readily available in drug stores. If the itching is extreme, you may need to consult your dermatologist for a prescription steroid, or antihistamine cream such as Zonalon®, which may cause drowsiness and should be used with caution. In some cases, your doctor may prescribe oral antihistamines like Atarax®, commonly used to treat allergic reactions and which may also cause drowsiness.

Mosquito bites should not be a problem for more than a week. If bites are not healing by then or if they are getting worse and interfere with your quality of life, see your doctor. Some skin conditions masquerade as bites and need different treatment. And some children have long-lasting reactions to insect bites and require treatment to keep them from getting worse. In these cases, I recommend trimming the child’s nails, using a topical medication, and covering the affected area with a Band-Aid® to reduce scratching until you can see a doctor. Avoiding future bites is especially important for the comfort of these children.

Take preventive medication

If you tend to have large or severe reactions to mosquito bites (skeeter syndrome), consider taking a nondrowsy, nonprescription antihistamine when you know you’ll be exposed to mosquitoes.

What’s a Mosquito?

A mosquito is an insect that is found all over the world. There are thousands of different kinds of mosquitoes in many different sizes and colors.

Female mosquitoes bite animals and humans and drink a very small amount of their blood. Female mosquitoes need protein and iron from blood to produce eggs. Female mosquito has a special part of her mouth that she uses to suck blood, and her saliva (spit) thins the blood so she can drink it. In fact, it’s the mosquito’s saliva that makes the bites itch!

After drinking blood, female mosquitoes find some standing water and lay their eggs in it. The eggs hatch into larvae, then pupae, and then they become adult mosquitoes. The male mosquitoes live for about a week to ten days, and the female mosquitoes can live up to several weeks. Some female mosquitoes can hibernate in the winter, and they can live for months.

Why do mosquito bites itch

Papular urticaria is a hypersensitivity reaction, most often in a young child due to mosquito bites and/or fleabites. Papular urticaria is thought to be an allergic reaction to insects in the environment. Often after a few months or years the person becomes desensitized to these insects and the reaction dies down. Affected individuals rarely notice the initial bite. The most common identified causes are insects that live on cats and dogs, particularly fleas and mites.

New bites are accompanied by reactivation of old ones and present as symmetrical crops of itchy urticated papules. Papular urticaria resolves with the development of immunological tolerance.

Mosquito bite allergy

Hypersensitivity to mosquito bites is defined as the appearance of intense skin reactive lesions and systemic symptoms subsequent to mosquito bites. The patient with hypersensitivity to mosquito bites may experience bulla, ulceration, necrosis and/or scarring at the bite site and systemic symptoms such as high fever, lymphadenopathy, hepatosplenomegaly, hepatic dysfunction, hematuria, and proteinuria 1). Most cases of hypersensitivity to mosquito bites reported thus far have been associated with chronic Epstein-Barr virus infection or natural killer cell leukemia/lymphoma 2), 3). The majority of patients are from Japan or Korea and less than 20 years of age.

Most cases of hypersensitivity to mosquito bites have been reported in Japanese patients in the first 2 decades of life, and these cases have illustrated a close relationship between mosquito allergies and chronic Epstein-Barr virus infection and natural killer cell leukemia/lymphoma. However, not all cases of HMB develop into natural killer cell leukemia/lymphoma. Shigekiyo et al. 4) reported a case of hypersensitivity to mosquito bites developing into mantle cell lymphoma, and Konuma et al. 5) and Seon et al. 6) also reported cases of hypersensitivity to mosquito bites that did not develop into NK/T-cell proliferative diseases. To date, 7 patients with hypersensitivity to mosquito bites have been reported in Korea, including 3 patients with lymphoid neoplasms such as NK cell lymphoma, Hodgkin’s lymphoma-like B-cell lymphoproliferative disorder, and marginal zone B-cell lymphoma 7).

What do mosquito bites look like

A person who gets bitten by a mosquito will notice a round pink or red bump that itches a lot.

More-severe reactions may be experienced by children, adults not previously exposed to the type of mosquito that bit them, and people with immune system disorders. In these people, mosquito bites sometimes trigger:

  • A large area of swelling and redness
  • Low-grade fever
  • Hives
  • Swollen lymph nodes

Children are more likely to develop a severe reaction than are adults, because many adults have had mosquito bites throughout their lives and become desensitized.

It’s very unusual for someone to have an allergic reaction to a mosquito bite. But if you develop an allergic reaction and feel dizzy or sick, tell an adult immediately. A doctor can treat allergic reactions with medicines.

Figure 1. Mosquito bites

what mosquito bites look like

Some types of mosquitoes can spread serious diseases.

See your doctor if you develop a rash, flu-like symptoms such as fever, chills, headaches, joint and muscle pains (swelling or stiffness), fatigue, depression and generally feel unwell.

Most mosquito bites can be managed by washing the area with soap and water and applying an antiseptic. Cold packs may help with local pain and swelling.

To lessen your chance of being bitten by mosquitoes (and midges), cover up as much skin as possible and stay inside in the early morning or at dusk. Use an insect repellent when you are out and about and there are mosquitoes around.

What health problems can mosquito bites cause?

Most mosquito bites are harmless, but there are times when they can be dangerous.

The ways that mosquito bites can affect humans include:

  • Causing itchy bumps, as an immune system response to the mosquito’s saliva. This is the most common reaction. The bumps usually go away after a day or two.
  • Causing allergic reactions, including blisters, large hives, and in rare cases, anaphylaxis. Anaphylaxis is a severe allergic reaction that affects the whole body. It is a medical emergency.
  • Spreading diseases to humans. Some of these diseases can be serious. Many of them do not have any treatments, and only a few have vaccines to prevent them. These diseases are more of a problem in Africa and other tropical areas of the world, but more of them are spreading to the United States. One factor is climate change, which makes the conditions in some parts of the United States more favorable to certain types of mosquitoes. Other reasons include increased trade with, and travel to, tropical and subtropical areas.

Which diseases can mosquito bites spread?

Diseases in which specific mosquito bites are the vector occur worldwide but are particularly prevalent in tropical and developing regions.

Common diseases spread by mosquito bites include:

  • Parasites: Malaria
  • Viral disease: Dengue fever, Chikungunya fever, Zika fever and West Nile virus

Malaria

Malaria is a serious mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, people with malaria may develop severe complications and die. In 2016 an estimated 216 million cases of malaria occurred worldwide and 445,000 people died, mostly children in the African Region. About 1,700 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from countries where malaria transmission occurs, many from sub-Saharan Africa and South Asia.

Malaria is sometimes fatal disease caused by a parasite that commonly infects a certain type of mosquito which feeds on humans. People who get malaria are typically very sick with high fevers, shaking chills, and flu-like illness. Although malaria can be a deadly disease, illness and death from malaria can usually be prevented.

First- and second-generation immigrants from malaria-endemic countries returning to their “home” countries to visit friends and relatives tend not to use appropriate malaria prevention measures and thus are more likely to become infected with malaria.

Between 1957 and 2015, in the United States, 63 outbreaks of locally transmitted mosquito-borne malaria have occurred; in such outbreaks, local mosquitoes become infected by biting persons carrying malaria parasites (acquired in endemic areas) and then transmit malaria to local residents.

Of the species of Anopheles mosquitoes found in the United States, the three species that were responsible for malaria transmission prior to elimination (Anopheles quadrimaculatus in the east, Anopheles freeborni in the west and Anopheles pseudopunctipennis along the U.S./Mexico border) are still prevalent; thus there is a constant risk that malaria could be reintroduced in the United States.

Malaria symptoms

Infection with malaria parasites may result in a wide variety of symptoms, ranging from absent or very mild symptoms to severe disease and even death. Malaria disease can be categorized as uncomplicated or severe (complicated). In general, malaria is a curable disease if diagnosed and treated promptly and correctly.

All the clinical symptoms associated with malaria are caused by the asexual erythrocytic or blood stage parasites. When the parasite develops in the erythrocyte, numerous known and unknown waste substances such as hemozoin pigment and other toxic factors accumulate in the infected red blood cell. These are dumped into the bloodstream when the infected cells lyse and release invasive merozoites. The hemozoin and other toxic factors such as glucose phosphate isomerase stimulate macrophages and other cells to produce cytokines and other soluble factors which act to produce fever and rigors and probably influence other severe pathophysiology associated with malaria.

Plasmodium falciparum-infected erythrocytes, particularly those with mature trophozoites, adhere to the vascular endothelium of venular blood vessel walls and do not freely circulate in the blood. When this sequestration of infected erythrocytes occurs in the vessels of the brain it is believed to be a factor in causing the severe disease syndrome known as cerebral malaria, which is associated with high mortality.

Incubation Period

Following the infective bite by the Anopheles mosquito, a period of time (the “incubation period”) goes by before the first symptoms appear. The incubation period in most cases varies from 7 to 30 days. The shorter periods are observed most frequently with Plasmodium falciparum and the longer ones with Plasmodium malariae.

Antimalarial drugs taken for prophylaxis by travelers can delay the appearance of malaria symptoms by weeks or months, long after the traveler has left the malaria-endemic area. This can happen particularly with Plasmodium vivax and Plasmodium ovale, both of which can produce dormant liver stage parasites; the liver stages may reactivate and cause disease months after the infective mosquito bite.

Such long delays between exposure and development of symptoms can result in misdiagnosis or delayed diagnosis because of reduced clinical suspicion by the health-care provider. Returned travelers should always remind their health-care providers of any travel in areas where malaria occurs during the past 12 months.

Uncomplicated Malaria

The classical (but rarely observed) malaria attack lasts 6-10 hours. It consists of:

  • a cold stage (sensation of cold, shivering)
  • a hot stage (fever, headaches, vomiting; seizures in young children)
  • and finally a sweating stage (sweats, return to normal temperature, tiredness).

Classically (but infrequently observed) the attacks occur every second day with the “tertian” parasites (Plasmodium falciparum, Plasmodium vivax, and Plasmodium ovale) and every third day with the “quartan” parasite (Plasmodium malariae).

More commonly, the patient presents with a combination of the following symptoms:

  • Fever
  • Chills
  • Sweats
  • Headaches
  • Nausea and vomiting
  • Body aches
  • General malaise

In countries where cases of malaria are infrequent, these symptoms may be attributed to influenza, a common cold or other common infections, especially if malaria is not suspected. Conversely, in countries where malaria is frequent, residents often recognize the symptoms as malaria and treat themselves without seeking diagnostic confirmation (“presumptive treatment”).

Physical findings may include:

  • Elevated temperatures
  • Perspiration
  • Weakness
  • Enlarged spleen
  • Mild jaundice
  • Enlargement of the liver
  • Increased respiratory rate

Diagnosis of malaria depends on the demonstration of parasites in the blood, usually by microscopy. Additional laboratory findings may include mild anemia, mild decrease in blood platelets (thrombocytopenia), elevation of bilirubin, and elevation of aminotransferases.

Severe Malaria

Severe malaria occurs when infections are complicated by serious organ failures or abnormalities in the patient’s blood or metabolism. The manifestations of severe malaria include:

  • Cerebral malaria, with abnormal behavior, impairment of consciousness, seizures, coma, or other neurologic abnormalities
  • Severe anemia due to hemolysis (destruction of the red blood cells)
  • Hemoglobinuria (hemoglobin in the urine) due to hemolysis
  • Acute respiratory distress syndrome (ARDS), an inflammatory reaction in the lungs that inhibits oxygen exchange, which may occur even after the parasite
  • counts have decreased in response to treatment
  • Abnormalities in blood coagulation
  • Low blood pressure caused by cardiovascular collapse
  • Acute kidney failure
  • Hyperparasitemia, where more than 5% of the red blood cells are infected by malaria parasites
  • Metabolic acidosis (excessive acidity in the blood and tissue fluids), often in association with hypoglycemia
  • Hypoglycemia (low blood glucose). Hypoglycemia may also occur in pregnant women with uncomplicated malaria, or after treatment with quinine.

Severe malaria is a medical emergency and should be treated urgently and aggressively.

Other Manifestations of Malaria

  • Neurologic defects may occasionally persist following cerebral malaria, especially in children. Such defects include trouble with movements (ataxia), palsies, speech difficulties, deafness, and blindness.
  • Recurrent infections with Plasmodium falciparum may result in severe anemia. This occurs especially in young children in tropical Africa with frequent infections that are inadequately treated.
  • Malaria during pregnancy (especially Plasmodium falciparum) may cause severe disease in the mother, and may lead to premature delivery or delivery of a low-birth-weight baby.
  • On rare occasions, P. vivax malaria can cause rupture of the spleen.
  • Nephrotic syndrome (a chronic, severe kidney disease) can result from chronic or repeated infections with Plasmodium malariae.
  • Hyperreactive malarial splenomegaly (also called “tropical splenomegaly syndrome”) occurs infrequently and is attributed to an abnormal immune response to repeated malarial infections. The disease is marked by a very enlarged spleen and liver, abnormal immunologic findings, anemia, and a susceptibility to other infections (such as skin or respiratory infections).

Malaria Relapses

In Plasmodium vivax and Plasmodium ovale infections, patients having recovered from the first episode of illness may suffer several additional attacks (“relapses”) after months or even years without symptoms. Relapses occur because Plasmodium vivax and Plasmodium ovale have dormant liver stage parasites (“hypnozoites”) that may reactivate. Treatment to reduce the chance of such relapses is available and should follow treatment of the first attack.

Malaria diagnosis

Malaria must be recognized promptly in order to treat the patient in time and to prevent further spread of infection in the community via local mosquitoes.

Malaria should be considered a potential medical emergency and should be treated accordingly. Delay in diagnosis and treatment is a leading cause of death in malaria patients in the United States.

Malaria can be suspected based on the patient’s travel history, symptoms, and the physical findings at examination. However, for a definitive diagnosis to be made, laboratory tests must demonstrate the malaria parasites or their components.

Microscopic diagnosis

Malaria parasites can be identified by examining under the microscope a drop of the patient’s blood, spread out as a “blood smear” on a microscope slide. Prior to examination, the specimen is stained (most often with the Giemsa stain) to give the parasites a distinctive appearance. This technique remains the gold standard for laboratory confirmation of malaria. However, it depends on the quality of the reagents, of the microscope, and on the experience of the laboratorian.

Diagnosis of malaria can be difficult:

  • Where malaria is not endemic any more (such as in the United States), health-care providers may not be familiar with the disease. Clinicians seeing a malaria patient may forget to consider malaria among the potential diagnoses and not order the needed diagnostic tests. Laboratorians may lack experience with malaria and fail to detect parasites when examining blood smears under the microscope.
  • In some malaria-endemic areas, malaria transmission is so intense that a large proportion of the population is infected but not made ill by the parasites. Such carriers have developed just enough immunity to protect them from malarial illness but not from malarial infection. In that situation, finding malaria parasites in an ill person does not necessarily mean that the illness is caused by the parasites.

Clinical diagnosis is based on the patient’s symptoms and on physical findings at examination.

The first symptoms of malaria (most often fever, chills, sweats, headaches, muscle pains, nausea and vomiting) are often not specific and are also found in other diseases (such as the “flu” and common viral infections). Likewise, the physical findings are often not specific (elevated temperature, perspiration, tiredness).

In severe malaria (caused by Plasmodium falciparum), clinical findings (confusion, coma, neurologic focal signs, severe anemia, respiratory difficulties) are more striking and may increase the index of suspicion for malaria.

If possible, clinical findings should always be confirmed by a laboratory test for malaria.

In addition to ordering the malaria specific diagnostic tests described below, the health-care provider should conduct an initial workup and request a complete blood count and a routine chemistry panel. In the event that the person does have a positive malaria test, these additional tests will be useful in determining whether the patient has uncomplicated or severe manifestations of the malaria infection. Specifically, these tests can detect severe anemia, hypoglycemia, renal failure, hyperbilirubinemia, and acid-base disturbances.

Antigen Detection

Various test kits are available to detect antigens derived from malaria parasites. Such immunologic (“immunochromatographic”) tests most often use a dipstick or cassette format, and provide results in 2-15 minutes. These “Rapid Diagnostic Tests” (RDTs) offer a useful alternative to microscopy in situations where reliable microscopic diagnosis is not available. Malaria RDTs are currently used in some clinical settings and programs.

On June 13, 2007, the U.S. Food and Drug Administration (FDA) approved the first Rapid Diagnostic Test for use in the United States. This Rapid Diagnostic Test is approved for use by hospital and commercial laboratories, not by individual clinicians or by patients themselves. It is recommended that all Rapid Diagnostic Tests are followed-up with microscopy to confirm the results and if positive, to quantify the proportion of red blood cells that are infected. The use of this Rapid Diagnostic Test may decrease the amount of time that it takes to determine that a patient is infected with malaria.

Molecular Diagnosis

Parasite nucleic acids are detected using polymerase chain reaction (PCR). Although this technique may be slightly more sensitive than smear microscopy, it is of limited utility for the diagnosis of acutely ill patients in the standard healthcare setting. Polymerase chain reaction (PCR) results are often not available quickly enough to be of value in establishing the diagnosis of malaria infection.

Polymerase chain reaction (PCR) is most useful for confirming the species of malarial parasite after the diagnosis has been established by either smear microscopy or Rapid Diagnostic Test.

Serology

Serology detects antibodies against malaria parasites, using either indirect immunofluorescence (IFA) or enzyme-linked immunosorbent assay (ELISA). Serology does not detect current infection but rather measures past exposure.

Drug Resistance Tests

Drug resistance tests must be performed in specialized laboratories to assess the susceptibility to antimalarial compounds of parasites collected from a specific patient. Two main laboratory methods are available:

In vitro tests: The parasites are grown in culture in the presence of increasing concentrations of drugs; the drug concentration that inhibits parasite growth is used as endpoint.

Molecular characterization: Molecular markers assessed by polymerase chain reaction (PCR) or gene sequencing also allow the prediction, to some degree, of resistance to some drugs. CDC recommends that all cases of malaria diagnosed in the United States should be evaluated for evidence of drug resistance.

Malaria treatment in United States

Malaria can be a severe, potentially fatal disease (especially when caused by Plasmodium falciparum) and treatment should be initiated as soon as possible.

Patients who have severe Plasmodium falciparum malaria or who cannot take oral medications should be given the treatment by continuous intravenous infusion.

Most drugs used in treatment are active against the parasite forms in the blood (the form that causes disease) and include:

  • chloroquine
  • atovaquone-proguanil (Malarone®)
  • artemether-lumefantrine (Coartem®)
  • mefloquine (Lariam®)
  • quinine
  • quinidine
  • doxycycline (used in combination with quinine)
  • clindamycin (used in combination with quinine)
  • artesunate (not licensed for use in the United States, but available through the CDC malaria hotline)

In addition, primaquine is active against the dormant parasite liver forms (hypnozoites) and prevents relapses. Primaquine should not be taken by pregnant women or by people who are deficient in G6PD (glucose-6-phosphate dehydrogenase). Patients should not take primaquine until a screening test has excluded G6PD deficiency.

How to treat a patient with malaria depends on:

  • The type (species) of the infecting parasite
  • The area where the infection was acquired and its drug-resistance status
  • The clinical status of the patient
  • Any accompanying illness or condition
  • Pregnancy
  • Drug allergies, or other medications taken by the patient.

Dengue fever

Dengue, or dengue fever, is a viral illness transmitted by the bite of any of dengue viruses. Patients with dengue usually present with fever, headache, rash, nausea, vomiting, aches and pains.

In some cases, dengue can progress to a severe form named severe dengue (previously known as dengue hemorrhagic fever), characterized by plasma leakage with or without hemorrhage. Severe hemorrhage or severe organ impairment can occur, with or without shock features 8).

There are an estimated 400 million infections in more than 100 countries around the world every year, especially in the tropical areas.

Children, the elderly and immunosuppressed individuals tend to be more prone to have atypical or severe forms of dengue virus infection. Severe dengue was first recognised in the 1950s during dengue epidemics in the Philippines and Thailand, but it is now reported worldwide.

The global spread and increasing severity of dengue were enabled by:

  • Increased population
  • International travel
  • Climate change with increasing temperatures in subtropical areas
  • More abundant mosquito breeding sites (small pools of fresh water like those in discarded tires, flower vases or uncapped water containers) 9).

Dengue virus belongs to the family of Flavivirus, the same family of viruses including yellow fever and zika. They are also called arboviruses, because are transmitted by arthropod bites (in the case of dengue by the Aedes mosquitoes, especially Aedes aegypti). Dengue viruses (DENV) are small, spherical, single-stranded enveloped RNA viruses with four distinct viral serotypes, DENV 1–4.

Once a person becomes infected, the virus is carried and multiplies in the blood, serving as a source of the virus for uninfected mosquitoes. Patients who are already infected with the dengue virus can transmit the infection via mosquitoes after the first symptoms appear until a maximum of two weeks later 10).

Dengue prevention

There is ongoing research about medications and vaccines against dengue virus, and also for reduction and/or elimination of Aedes mosquitoes [1,6].

Vector control

Mosquito breeding sites should be eliminated or controlled. The dengue virus-carrying mosquito often breeds in artificial containers and receptacles containing water.

The following measures can be taken to reduce the breeding of mosquitoes:

  • Cover all water tanks, cisterns, barrels, rubbish containers.
  • Remove or empty water in old tyres, tin cans, bottles, trays.
  • Check and clean out clogged gutters and flat roofs where water may have settled.
  • Change water regularly in pet water dishes, birdbaths and plant trays.
  • Introduce larvivorous fish (such as guppy) to ornamental water features, as these eat mosquito larvae.
  • Trim weeds and tall grasses, as adult mosquitoes seek these for shade.

People should avoid being bitten by mosquitoes.

  • Wear long sleeves and pants.
  • Install secure screens to windows and doors to keep mosquitoes out.
  • Use an insect repellent such as DEET.
  • Sleep under mosquito curtains or nets, this is particularly important when children are sleeping or resting during daylight hours.
  • In high-risk areas, insecticide sprays may be used to kill mosquitoes.

Dengue signs and symptoms

A person infected by the dengue virus develops severe flu-like symptoms. The clinical features of dengue fever vary according to the characteristics of the infected individual. Symptoms usually last for 2–7 days, after an incubation period of 4–10 days after the bite from an infected mosquito [1,3].

In 2009, the World Health Organization re-classified dengue infections as dengue fever and divided it into three groups 11).

Probable dengue fever: fever (usually up to 40°C) plus two of the following:

  • Nausea and/or vomiting
  • Rash (red and confluent dots and blotches)
  • Leukopenia (low white blood cells)
  • Aches and pains (‘break-bone’) especially arms and legs
  • Positive tourniquet test (a test performed by doctors)
  • Retro-ocular headache (pain behind the eyes).

Dengue fever with warning signs:  dengue fever plus at least one of the following:

  • Abdominal pain or tenderness
  • Persisting vomiting
  • Mucosal bleeding (from nose and gums)
  • Lethargy (somnolence) or restlessness
  • Hepatomegaly (enlarged liver)
  • Increased hematocrit (feature of fluid loss)
  • Thrombocytopenia (low platelet count)
  • Pleural or peritoneal effusion (fluid in the lining of the lungs or the abdominal organs).

Severe dengue: dengue fever plus at least one of the following:

  • Kidney failure
  • Acute pulmonary edema (sudden accumulation of fluid in the lungs)
  • Shock features (low blood pressure, rapid heart rate)
  • Severe bleeding
  • Heart failure AST or ALT > 1000 IU (very abnormal liver function tests)
  • Altered consciousness level (drowsiness or even coma).

The most feared complication of dengue is its severe form. Major bleeding, profound shock, multiple organ failure and brain or heart damage can usually lead to death when present. This is fortunately uncommon 12).

Dengue diagnosis

Dengue infection is diagnosed by testing blood samples during the first 5 days of symptoms and/or early recovery phase (more than 5 days of symptoms) confirming the presence of the virus. The diagnosis can also be confirmed by:

  • The presence of IgM against dengue virus (IgM is an antibody produced in acute infections); or;
  • The increase in IgG titres against dengue virus in two different blood samples (IgG is an antibody produced when the person has been infected before) 13).

Dengue treatment

There is no specific treatment for dengue fever. Patients should seek medical advice, rest and drink plenty of fluids.

  • Paracetamol (acetaminophen) can be taken to bring down fever and reduce joint pains.
  • Aspirin or non-steroidal anti-inflammatories (NSAIDs) such as ibuprofen should not be taken since they can increase the risk of bleeding [1,5].

In the case of severe dengue, the patient should be admitted to hospital for maintenance of the patient’s circulating fluid volume and management of hemorrhagic complications.

Dengue outcome (prognosis)

After recovery from dengue fever, the person develops lifelong immunity against that particular dengue virus serotype, but confers only partial and transient protection against the other three serotypes of the virus.

Sequential infections seem to increase the risk of developing severe dengue. The person with non-complicated dengue fever recovers without any residual problem 14).

Chikungunya fever

Chikungunya fever is a re-emerging viral illness that is spread from human-to-human by the bite of virus-carrying mosquitoes. The disease is mostly confined to people living in tropical Africa and Asia and is characterized by a sudden and severe fever, skin rash and joint and muscle pain.

The chikungunya virus (CHIK V) is a RNA virus belonging to family Togaviridae, genus Alphavirus. It was first discovered in Africa in 1952-1953 and later introduced into Asia.

The African and Asian strains of CHIK V differ biologically and spread of the virus occurs differently. In Asia, the mosquitoes Aedes aegypti and Aedes albopictus are the two main species involved in transmitting the virus from infected individuals to healthy contacts. In particular, Aedes aegypti breed in and around where humans live and usually bite during daylight hours. In Africa, CHIK V appears to be maintained in a cycle involving wild primates such as monkeys and baboons and forest dwelling species of Aedes mosquitoes.

Major epidemics or outbreaks of chikungunya fever occur cyclically, a disease-free period of several years or decades may exist between the outbreaks. For example, a well-documented outbreak of the disease occurred in parts of India in 1963, 1964 and 1973. For the last 30 years there have been few reported cases, however, in 2005 several states in India have reported outbreaks of the disease and the outbreak is still continuing.

Chikungunya fever prevention

The best way to prevent chikungunya fever is by preventing spread of the virus by vector control. This means eliminating or controlling mosquito breeding sites. The CHIK V-carrying mosquito likes to breed in artificial containers and receptacles containing water.

The following measures can be taken to reduce the breeding of mosquitoes:

  • Cover tightly with a lid all water tanks, cisterns, barrels, rubbish containers, etc.
  • Remove or empty water in old tyres, tin cans, bottles, trays, etc.
  • Check and clean out clogged gutters and flat roofs where water may have settled.
  • Change water regularly in pet water dishes, birdbaths and plant trays.
  • Introduce larvivorous fish (e.g. guppy) to ornamental water features as these eat the mosquito larvae.
  • Trim weeds and tall grasses as adult mosquitoes seek these for shade on hot days.

People can do the following to prevent themselves from being bitten by mosquitoes:

  • Wear long sleeves and pants.
  • Install secure screens to windows and doors to keep mosquitoes out.
  • Use an insect repellent such as DEET.
  • Sleep under mosquito curtains or nets, this is particularly important when children are sleeping or resting during daylight hours.
  • In high-risk areas insecticide sprays may be used to kill mosquitoes.

Chikungunya fever signs and symptoms

Infection with the CHIK virus begins with a short incubation period of 2-4 days. At about 48 hours after being bitten by a virus-carrying mosquito, patients will experience sudden high fever with shaking chills. Some patients also get a maculopapular rash (red flat patches that may contain small raised spots) over the trunk, limbs and face. This tends to last 3 or 4 days. Commonly patients will experience severe myalgia (muscle pain) and arthralgia (joint pain). Joint pain initially starts in the small joints of the hands and feet, wrists and ankles, and later the larger joints. Other non-specific symptoms may include headache, slight photophobia and insomnia.

Cutaneous manifestations of chikungunya fever

With the current outbreak in India several studies have been conducted on chikungunya fever. One study observed 145 “suspect cases” of chikungunya fever over a 3-month period and focused on the skin manifestations of the disease 15).

Some of their findings are listed below:

  • In the majority of cases skin problems developed in the very early stages of the illness. Approximately 73% of patients developed skin lesions during the acute phase of the illness (within 7 days), accompanying high fever and severe muscle and joint pain. 32% developed skin problems after the fever had gone but muscle and joint pain were still present (within 1 month), and a handful of patients (8%) developed skin problems more than 1 month after the acute illness.
  • The most common skin problem was a brownish-black colouring over the centre of the face. This appeared as freckle-like spots or as a diffuse, slate-coloured pigmentation. Sometimes skin discolouration would also extend to the trunk, limbs, hands and feet.
  • In 24% of patients, all of whom were male, multiple aphthous-like ulcers developed in the groin area. These occurred during the acute illness and were preceded by redness, swelling and pain of the scrotum and groin region. Ulceration on the vulva in women have occasionally been reported in other outbreaks.
  • A few infants developed blisters in association with high fever. These ruptured easily but healed without any problems.
  • Other skin conditions have included tenderness/edema of hands and feet, fixed drug eruptions, erythema nodosum, erythema multiforme and urticaria.
  • Flare-ups of existing skin problems such as psoriasis or lichen planus occurred in a few patients following the acute illness.

Chikungunya fever treatment

There is no vaccine or specific treatment available against CHIK V infection. Fortunately, the illness is usually self-limiting and resolves with time. Supportive therapy with antipyretics and nonsteroidal anti-inflammatory drugs (NSAIDs) are used to control fever and joint pain. Fever usually disappears after 2-3 days. Muscle and joint pain, which can be very severe usually lasts for about 5-7 days but in some cases may linger for much longer periods. Elderly patients in particular may suffer muscle and joint pain for several months.

Skin discolouration and rash can be treated with sunscreens and topical corticosteroids. Skin rash on the face appears to resolve completely within about 3 weeks, whilst resolution is a little longer when other parts of the body are affected. Ulcers should be cleaned and treated with topical antimicrobials to prevent secondary infections. These usually heal within 7-10 days. More severe lesions may require systemic steroid treatment.

Zika fever

Zika virus causes an infection that is mainly spread by the bite of tropical zika virus-carrying mosquitoes. It presents as a flu-like illness rather similar to dengue fever, but not as severe. An itchy rash is a prominent feature. It also causes neurological symptoms due to small fiber neuropathy.

If you have Zika, protect others

  • During the first week of infection, Zika virus can be found in the blood and passed from an infected person to another mosquito through mosquito bites. An infected mosquito can then spread the virus to other people.
  • Zika can be passed through sex from a person who has Zika to his or her partners. Sex includes vaginal, anal and oral sex, and the sharing of sex toys.

Birth defects have been reported after zika infection of pregnant women 16). Pregnant women should take special precautions if traveling to affected areas 17).

  • Zika infection during pregnancy can cause serious birth defects and is associated with other pregnancy problems.
  • Several countries that have experienced Zika outbreaks recently have reported increases in people who have Guillain-Barré syndrome.
  • Current Centers for Disease Control and Prevention research suggests that Guillain-Barré syndrome is strongly associated with Zika; however, only a small proportion of people with recent Zika virus infection get Guillain-Barré syndrome.

Guillain-Barré syndrome is an uncommon sickness of the nervous system in which a person’s own immune system damages the nerve cells, causing muscle weakness, and sometimes, paralysis.

Guillain-Barré syndrome symptoms include weakness of the arms and legs and, in severe cases, can affect the muscles that control breathing.

These symptoms can last a few weeks or several months. Most people fully recover from Guillain-Barré syndrome, though some people have permanent damage. Very few people die from Guillain-Barré syndrome. Researchers do not fully understand what causes Guillain-Barré syndrome. Most people with Guillain-Barré syndrome report an infection before they have Guillain-Barré syndrome symptoms. Rarely, vaccination has also been associated with the onset of Guillain-Barré syndrome (for example, the 1976 Swine influenza vaccine).

An estimated 3,000 to 6,000 people, or 1-2 cases for every 100,000 people, develop Guillain-Barré syndrome each year in the US. Most cases of Guillain-Barré syndrome tend to occur for no known reason, and true “clusters” of cases of Guillain-Barré syndrome are very unusual.

Zika and Microcephaly

Microcephaly is a birth defect in which a baby’s head is smaller than expected when compared to babies of the same sex and age. Babies with microcephaly often have smaller brains that might not have developed properly.

Zika virus infection during pregnancy is a cause of microcephaly. During pregnancy, a baby’s head grows because the baby’s brain grows. Microcephaly can occur because a baby’s brain has not developed properly during pregnancy or has stopped growing after birth.

Congenital Zika Syndrome

Congenital Zika syndrome is a unique pattern of birth defects found among fetuses and babies infected with Zika virus during pregnancy. Congenital Zika syndrome is described by the following five features:

  • Severe microcephaly where the skull has partially collapsed
  • Decreased brain tissue with a specific pattern of brain damage
  • Damage (i.e., scarring, pigment changes) to the back of the eye
  • Joints with limited range of motion, such as clubfoot
  • Too much muscle tone restricting body movement soon after birth

Babies who were infected with Zika before birth may have damage to their eyes and/or the part of their brain that is responsible for vision, which may affect their visual development. Both babies with and without microcephaly can have eye problems. If your baby was born with congenital Zika infection, he or she should receive the recommended screenings and tests to check for eye and other health problems, even if your baby appears healthy.

Not all babies born with congenital Zika infection will have all of these problems. Some infants with congenital Zika virus infection who do not have microcephaly at birth may later experience slowed head growth and develop postnatal microcephaly.

Recognizing that Zika is a cause of certain birth defects does not mean that every pregnant woman infected with Zika will have a baby with a birth defect. It means that infection with Zika during pregnancy increases the chances for these problems. Scientists continue to study how Zika virus affects mothers and their children to better understand the full range of potential health problems that Zika virus infection during pregnancy may cause.

Future Pregnancies

Based on the available evidence, we think that Zika virus infection in a woman who is not pregnant would not pose a risk for birth defects in future pregnancies after the virus has cleared from her blood. From what scientists know about similar infections, once a person has been infected with Zika virus, he or she is likely to be protected from a future Zika infection.

Who gets zika virus infection?

Zika virus affects people that have travelled to affected tropical areas and have been bitten by a mosquito that carries the infection. It is estimated that only about one in five people carrying the virus actually develop symptoms from zika virus infection.

For current affected areas worldwide, see Zika-affected areas information on the US Centers for Disease Control and Prevention website 18). During 2014–2016, these have included the Pacific Islands, South East Asia, Central and South American countries.

CDC has identified two types of geographic areas to describe where Zika virus-related domestic guidance applies: Zika active transmission areas (designated as red areas) and Zika cautionary areas (designated as yellow areas).

Red Areas

A Zika active transmission (red) area is a geographic area where local, state, and CDC officials have identified the presence of confirmed, multi-person local mosquito-borne transmission and have determined that the intensity of Zika virus transmission presents a significant risk of contracting mosquito-borne Zika and poses a risk to pregnant women and blood and tissue safety.

  • Pregnant women should not travel to red areas.
  • Women and men who are planning to conceive in the near future should avoid nonessential travel to red areas.

Yellow Areas

A Zika cautionary (yellow) area is a geographic area where local mosquito-borne transmission has been identified and pregnant women and blood and tissue safety are at some undetermined risk, but evidence is lacking on whether the intensity of transmission is widespread and sustained.

  • Pregnant women should consider postponing travel to yellow areas.
  • Healthcare providers should discuss reproductive life plans with patients who are planning to conceive in the near future about the lower likelihood of Zika infection in yellow areas compared to red areas and the limited information about periconceptional infection risk.

Prevention

  • Pregnant women and their partners who live in or travel to red or yellow areas should be counseled to consistently and correctly use condoms every time they have sex (including vaginal, anal, and oral sex) to prevent Zika virus infection or they should not have sex during the pregnancy.
  • Couples in which one or both partners have had exposure1 who want to reduce their risk for spreading Zika through sex to the uninfected partner should be advised to use condoms consistently and correctly or abstain from sex for:
    • At least 8 weeks after symptom onset or last possible Zika virus exposure, (if only the woman was exposed), or
    • At least 6 months after symptom onset or last possible Zika virus exposure (if the man was exposed)
  • If couples are asymptomatic and possible exposure to Zika is ongoing, Healthcare providers should discuss reproductive life plans with their patients.
    • All women and men who live in or travel to red or yellow areas should be advised to remain aware of Zika virus transmission and strictly follow steps to prevent mosquito bites.
  • All travelers to red or yellow areas should be advised to use insect repellent for 3 weeks after returning home to prevent passing Zika to mosquitoes that could infect others.
  • All travelers to red or yellow areas should be counseled on the potential consequences of Zika virus infection to the fetus during pregnancy and the traveler’s role in preventing transmission to pregnant women in their communities.

Testing

Symptomatic

  • Pregnant women should be offered testing for Zika virus infection. There are limitations to the interpretation of laboratory tests done on specimens drawn more than 12 weeks after the start date of the exposure.
  • Men and non-pregnant women should be tested 19) for Zika virus infection based on time of evaluation relative to symptom onset. There are limitations to the interpretation of laboratory tests done on specimens drawn more than 12 weeks after the start date of the exposure.

Asymptomatic with ongoing exposure

  • Pregnant women should be offered testing for Zika virus infection.
  • Testing is not recommended for men and non-pregnant women. Zika virus testing is not recommended for asymptomatic non-pregnant persons with possible exposure to Zika virus because there is potential for false reassurance in the following ways: 1) a blood test may be performed after the virus is no longer in the blood but could still be present in semen, 2) the antibody test may be performed early after infection when the antibody levels are not yet high enough to be detected, 3) the antibody test may be performed later after infection when the antibody levels have fallen to undetectable levels, and 4) a test result can sometimes be negative in the setting of true infection.

Asymptomatic without ongoing exposure

Jurisdictional recommendations may take into account the epidemiology of Zika virus transmission and other epidemiologic considerations (e.g., seasonality and mosquito surveillance and control factors) in areas with risk for Zika virus transmission. Therefore, jurisdictions might include a routine recommendation to test asymptomatic pregnant women, particularly in areas where local, state, and CDC officials have identified the presence of confirmed, multi-person local mosquito-borne transmission and have determined that the intensity of Zika virus transmission presents a significant risk of Zika virus infection, posing a risk to pregnant women and blood and tissue safety (red areas). Please contact your state health department for state-specific guidance. Testing is not recommended for men and non-pregnant women.

Please note: Healthcare providers should contact their state, local, or territorial health department to coordinate testing and interpret results. Healthcare providers should discuss the limitations of laboratory tests used to diagnose Zika virus infection with their patients.

Preconception Counseling

With Zika symptoms and/or diagnosis: Women and men who are planning to conceive in the near future should be advised to wait at least 8 weeks if a woman had Zika symptoms and/or diagnosis, and at least 6 months if a man had Zika symptoms and/or diagnosis, before attempting conception.

No Zika symptoms, and without ongoing exposure (Red Areas)

Women and men who are planning to conceive in the near future should be advised to wait at least 8 weeks if only the woman was exposed and at least 6 months if the man was exposed after the end date of the last possible exposure before attempting conception.

No Zika symptoms, and without ongoing exposure (Yellow Areas)

Women and men who are planning to conceive in the near future should consider waiting at least 8 weeks if only the woman was exposed and at least 6 months if the man was exposed after the end date of the last possible exposure before attempting conception.

No Zika symptoms and with ongoing exposure

  • Women and men who are planning to conceive in the near future should be counseled on the possible risk for Zika virus infection during the periconceptional period and about the potential consequences of Zika virus infection to the fetus during pregnancy. Healthcare providers should discuss reproductive life plans with patients and review factors that might influence pregnancy timing (e.g., duration of Zika virus outbreak, fertility, age, reproductive history, medical history, personal values and preferences).
  • Women and men who live in or travel to red or yellow areas should be advised to remain aware of Zika virus transmission and strictly follow steps to prevent mosquito bites.

Please note: There are limited data about the persistence of Zika virus RNA in body fluids and the risk for adverse pregnancy outcomes associated with maternal Zika virus infection around the time of conception is currently unknown. Therefore, some couples in which one or both partners have had possible Zika virus exposure might choose to wait longer or shorter than the recommended period to conceive, depending on individual circumstances (e.g., age, fertility, details of possible exposure) and risk tolerance. Healthcare providers should work with couples to help them make informed decisions.

Zika virus infection prevention

The best way to prevent zika virus infections is by preventing spread of the virus by vector control. This means eliminating or controlling mosquito breeding sites. The zika virus-carrying mosquito likes to breed in artificial containers and receptacles containing water in and near buildings. The following measures can be taken to reduce the breeding of mosquitoes.

  • Cover tightly with a lid all water tanks, cisterns, barrels, rubbish containers, etc.
  • Remove or empty water in old tyres, tin cans, bottles, trays, etc.
  • Check and clean out clogged gutters and flat roofs where water may have settled.
  • Change water regularly in pet water dishes, birdbaths and plant trays.
  • Introduce larvivorous fish (e.g., guppy) to ornamental water features as these eat the mosquito larvae.
  • Trim weeds and tall grasses as adult mosquitoes seek these for shade on hot days.

People can do the following to prevent themselves from being bitten by mosquitoes:

  • The mosquitoes that can spread Zika are found throughout the United States.
  • Prevent Zika by avoiding mosquito bites.
  • Mosquitoes that spread Zika virus bite during the day and night.
  • Mosquitoes that spread Zika virus also spread dengue and chikungunya viruses.
  • Local mosquito-borne Zika virus transmission has been reported in the continental United States.
  • Wear long sleeves and pants.
  • Install secure screens to windows and doors to keep mosquitoes out.
  • Use an insect repellent such as DEET.
  • Sleep under mosquito curtains or nets, this is particularly important when children are sleeping or resting during daylight hours.
  • In high-risk areas, insecticide sprays may be used to kill mosquitoes.
  • Children must be protected too.

Zika can be passed through sex from a person who has Zika to his or her sex partners. Condoms can reduce the chance of getting Zika from sex. Condoms include male and female condoms.

Protect yourself during sex

  • Zika can be passed through sex from a person who has Zika to his or her sex partners.
  • Studies are underway to find out how long Zika stays in the semen and vaginal fluids of people who have Zika, and how long it can be passed to sex partners. We know that Zika can remain in semen longer than in other body fluids, including vaginal fluids, urine, and blood.

What you can do

  • Not having sex can eliminate the risk of getting Zika from sex.
  • Condoms can reduce the chance of getting Zika from sex.
    • Condoms include male and female condoms.
    • To be effective, condoms should be used from start to finish, every time during vaginal, anal, and oral sex and the sharing of sex toys.
    • Dental dams (latex or polyurethane sheets) may also be used for certain types of oral sex (mouth to vagina or mouth to anus).

No vaccine exists to prevent Zika. Vaccines to prevent zika virus infection are in development.

Zika virus diagnosis

Zika virus infection are diagnosed by typical clinical symptoms after mosquito bite in an endemic area. The infection is confirmed by specific serological tests for zika virus immunoglobulins (IgG and IgM), which may need to be repeated 2–3 weeks later. There is some cross-reactivity with tests for dengue viruses.

In US, zika virus infection is notifiable.

Zika virus infection treatment

There is no specific treatment available against zika virus infection.

Zika virus infection is usually self-limiting and resolves with supportive therapy. Paracetamol (acetaminophen) may be used to treat patients with fever. Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) are not recommended. Drink plenty of fluids, and take rest.

People with zika virus infection or who have recently had zika virus infection should not donate blood, as the virus could be transmitted to a recipient. They must also be careful to avoid mosquito bites to reduce spreading the disease to others.

West Nile virus

West Nile virus is an infectious disease that first appeared in the United States in 1999. Infected mosquitoes spread the virus that causes it. Most people infected with West Nile virus will have no symptoms or mild symptoms. About 1 in 5 people infected will develop a fever with other symptoms. The symptoms include a fever, headache, body aches, skin rash, and swollen lymph glands. They can last a few days to several weeks, and usually go away on their own.

Less than 1 percent of those infected will develop a serious, sometimes fatal, neurologic illness.

If West Nile virus enters the brain, however, it can be life-threatening. It may cause inflammation of the brain, called encephalitis, or inflammation of the tissue that surrounds the brain and spinal cord, called meningitis. A physical exam, health history and laboratory tests can diagnose it.

Older people and those with weakened immune systems are most at risk. There are no specific vaccines or treatments for human West Nile virus disease.

The best way to avoid West Nile virus is to prevent mosquito bites:

  • Use insect repellent
  • Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets or barrels
  • Stay indoors between dusk and dawn, when mosquitoes are most active
  • Use screens on windows to keep mosquitoes out

West Nile virus symptoms

No symptoms in most people. Most people (8 out of 10) infected with West Nile virus do not develop any symptoms.

Febrile illness (fever) in some people. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Serious symptoms in a few people. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).

  • Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.
  • Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.
  • Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent.
  • About 1 out of 10 people who develop severe illness affecting the central nervous system die.

West Nile virus diagnosis

  • See your healthcare provider if you develop the symptoms described above.
  • Your healthcare provider can order tests to look for West Nile virus infection.

West Nile virus Antibody Testing

Laboratory diagnosis is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect West Nile virus-specific IgM antibodies. Immunoassays for West Nile virus-specific IgM are available commercially and through state public health laboratories.

West Nile virus-specific IgM antibodies are usually detectable 3 to 8 days after onset of illness and persist for 30 to 90 days, but longer persistence has been documented. Therefore, positive IgM antibodies occasionally may reflect a past infection. If serum is collected within 8 days of illness onset, the absence of detectable virus-specific IgM does not rule out the diagnosis of West Nile virus infection, and the test may need to be repeated on a later sample.

The presence of West Nile virus-specific IgM in blood or CSF provides good evidence of recent infection but may also result from cross-reactive antibodies after infection with other flaviviruses or from non-specific reactivity. According to product inserts for commercially available West Nile virus IgM assays, all positive results obtained with these assays should be confirmed by neutralizing antibody testing of acute- and convalescent-phase serum specimens at a state public health laboratory or CDC.

West Nile virus IgG antibodies generally are detected shortly after IgM antibodies and persist for many years following a symptomatic or asymptomatic infection. Therefore, the presence of IgG antibodies alone is only evidence of previous infection and clinically compatible cases with the presence of IgG, but not IgM, should be evaluated for other etiologic agents.

Plaque-reduction neutralization tests (PRNTs) performed in reference laboratories, including some state public health laboratories and CDC, can help determine the specific infecting flavivirus. PRNTs can also confirm acute infection by demonstrating a fourfold or greater change in West Nile virus-specific neutralizing antibody titer between acute- and convalescent-phase serum samples collected 2 to 3 weeks apart.

Other testing for West Nile virus disease

Viral cultures and tests to detect viral RNA (e.g., reverse transcriptase-polymerase chain reaction [RT-PCR]) can be performed on serum, CSF, and tissue specimens that are collected early in the course of illness and, if results are positive, can confirm an infection. Immunohistochemistry (IHC) can detect West Nile virus antigen in formalin-fixed tissue. Negative results of these tests do not rule out West Nile virus infection. Viral culture, reverse transcriptase-polymerase chain reaction, and immunohistochemistry can be requested through state public health laboratories or CDC.

West Nile virus treatment

  • No vaccine or specific antiviral treatments for West Nile virus infection are available.
  • Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms
  • In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.
  • If you think you or a family member might have West Nile virus disease, talk with your health care provider.

Protection Against Mosquito Bites

Vaccines or prophylactic drugs are available to protect against some vectorborne diseases such as yellow fever, Japanese encephalitis, and malaria; however, travelers are advised to use repellents and other general protective measures against biting insects. The effectiveness of malaria prophylaxis is variable, depending on patterns of drug resistance, bioavailability, and compliance with medication, and no similar preventive measures exist for other mosquito borne diseases such as dengue, chikungunya, Zika, and West Nile encephalitis, or tickborne diseases such as Lyme borreliosis, tickborne encephalitis, and relapsing fever.

General Protective Measures

Avoid outbreaks. To the extent possible, travelers should avoid known foci of epidemic disease transmission.

Wear appropriate clothing. Travelers can minimize areas of exposed skin by wearing long-sleeved shirts, long pants, boots, and hats. Tucking in shirts, tucking pants into socks, and wearing closed shoes instead of sandals may reduce risk. Repellents or insecticides, such as permethrin, can be applied to clothing and gear for added protection.

Bed nets. When accommodations are not adequately screened or air conditioned, bed nets are essential in providing protection and reducing discomfort caused by biting insects. If bed nets do not reach the floor, they should be tucked under mattresses. Bed nets are most effective when they are treated with a pyrethroid insecticide. Pretreated, long-lasting bed nets can be purchased before traveling, or nets can be treated after purchase. Effective, treated nets may also be available in destination countries. Nets treated with a pyrethroid insecticide will be effective for several months if they are not washed. Long-lasting pretreated nets may be effective for much longer.

Insecticides and spatial repellents. More spatial repellent products are becoming commercially available. These products, containing active ingredients such as metofluthrin and allethrin, augment aerosol insecticide sprays, vaporizing mats, and mosquito coils that have been available for some time. Such products can help to clear rooms or areas of mosquitoes (spray aerosols) or repel mosquitoes from a circumscribed area (coils, spatial repellents). Although many of these products appear to have repellent or insecticidal activity under particular conditions, they have not yet been adequately evaluated in peer-reviewed studies for their efficacy in preventing vectorborne disease. Travelers should supplement the use of these products with repellent on skin or clothing and using bed nets in areas where vector-borne diseases are a risk or biting arthropods are noted. Since some products available internationally may contain pesticides that are not registered in the United States, it may be preferable for travelers to bring their own. Insecticides and repellent products should always be used with caution, avoiding direct inhalation of spray or smoke.

Maximizing protection from mosquitoes and ticks

To optimize protection against mosquitoes and ticks and reduce the risk of diseases they transmit:

  • Wear a long-sleeved shirt, long pants, and socks.
  • Treat clothing with permethrin or purchase pretreated clothing.
  • Permethrin-treated clothing will retain repellent activity through multiple washes.
  • Repellents used on skin can also be applied to clothing but provide shorter duration of protection (same duration as on skin) and must be reapplied after laundering.
  • Apply lotion, liquid, or spray repellent to exposed skin.

For Mosquitoes

  • Ensure adequate protection during times of day when mosquitoes are most active.
  • Dengue, yellow fever, Zika, and chikungunya vector mosquitoes bite mainly from dawn to dusk.
  • Malaria, West Nile, and Japanese encephalitis vector mosquitoes bite mainly from dusk to dawn.
  • Use common sense. Reapply repellents as protection wanes and mosquitoes start to bite.

Repellents for Use on Skin and Clothing

The Centers for Disease Control and Prevention (CDC) has evaluated information published in peer-reviewed scientific literature and data available from the United States Environmental Protection Agency (EPA) to identify several types of EPA-registered products that provide repellent activity sufficient to help people reduce the bites of disease-carrying mosquitoes 20). Products containing the following active ingredients typically provide reasonably long-lasting protection:

  • DEET (chemical name: N,N-diethyl-m-toluamide or N,N-diethyl-3-methyl-benzamide). Products containing DEET include, but are not limited to, Off!, Cutter, Sawyer, and Ultrathon.
  • Picaridin (KBR 3023 [Bayrepel] and icaridin outside the US; chemical name: 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester). Products containing picaridin include, but are not limited to, Cutter Advanced, Skin So Soft Bug Guard Plus, and Autan (outside the US).
  • Oil of lemon eucalyptus (OLE) or PMD (chemical name: para-menthane-3,8-diol), the synthesized version of OLE. Products containing OLE and PMD include, but are not limited to, Repel and Off ! Botanicals. This recommendation refers to EPA-registered products containing the active ingredient OLE (or PMD). “Pure” oil of lemon eucalyptus (essential oil not formulated as a repellent) is not recommended; it has not undergone similar, validated testing for safety and efficacy and is not registered with EPA as an insect repellent.
  • IR3535 (chemical name: 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester). Products containing IR3535 include, but are not limited to, Skin So Soft Bug Guard Plus Expedition and SkinSmart.
  • 2-undecanone (chemical name: methyl nonyl ketone). The product BioUD contains 2-undecanone.

The United States Environmental Protection Agency (EPA) characterizes the active ingredients DEET and picaridin as “conventional repellents” and OLE, PMD, IR3535, and 2-undecanone as “biopesticide repellents,” which are either derived from or are synthetic versions of natural materials.

Used according to package directions, these products are generally safe for children and adults, with a few exceptions:

  • Don’t use DEET-containing products on infants younger than 2 months.
  • Don’t let young children get DEET or icaridin-containing products on their hands or faces.
  • Don’t use oil of lemon eucalyptus on children under age 3 years.
  • Don’t apply repellent under clothing.
  • Don’t apply repellent over sunburns, cuts, wounds or rashes.
  • When you go indoors, wash with soap and water to remove any remaining repellent.

Repellent Efficacy

Published data indicate that repellent efficacy and duration of protection vary considerably among products and among mosquito and tick species. Product efficacy and duration of protection are also markedly affected by ambient temperature, level of activity, amount of perspiration, exposure to water, abrasive removal, and other factors. In general, higher concentrations of active ingredient provide longer duration of protection, regardless of the active ingredient. Products with <10% active ingredient may offer only limited protection, often 1–2 hours. Products that offer sustained-release or controlled-release (microencapsulated) formulations, even with lower active ingredient concentrations, may provide longer protection times. Studies suggest that concentrations of DEET above approximately 50% do not offer a marked increase in protection time against mosquitoes; DEET efficacy tends to plateau at a concentration of approximately 50%. The Centers for Disease Control and Prevention (CDC) recommends using products with ≥20% DEET on exposed skin to reduce biting by ticks that may spread disease.

Recommendations are based on peer-reviewed journal articles and scientific studies and data submitted to regulatory agencies. People may experience some variation in protection from different products. Regardless of what product is used, if travelers start to get insect bites they should reapply the repellent according to the label instructions, try a different product, or, if possible, leave the area with biting insects.

Ideally, repellents should be purchased before traveling and can be found online or in hardware stores, drug stores, and supermarkets. A wide variety of repellents can be found in camping, sporting goods, and military surplus stores. When purchasing repellents overseas, look for the active ingredients specified above on the product labels; some names of products available internationally have been specified in the list above.

Repellents and Insecticides for Use on Clothing

Clothing, hats, shoes, bed nets, jackets, and camping gear can be treated with permethrin for added protection. Products such as Permanone and Sawyer, Permethrin, Repel, and Ultrathon Permethrin Clothing Treatment are registered with EPA specifically for use by consumers to treat clothing and gear. Alternatively, clothing pretreated with permethrin is commercially available, marketed to consumers in the United States as Insect Shield, BugsAway, or Insect Blocker.

Permethrin is a highly effective insecticide, acaricide and repellent. Permethrin-treated clothing repels and kills ticks, chiggers, mosquitoes, and other biting and nuisance arthropods. Clothing and other items must be treated 24–48 hours in advance of travel to allow them to dry. As with all pesticides, follow the label instructions when using permethrin clothing treatments.

Permethrin-treated materials retain repellency or insecticidal activity after repeated laundering but should be retreated, as described on the product label, to provide continued protection. Clothing that is treated before purchase is labeled for efficacy through 70 launderings. Clothing treated with the other repellent products described above (such as DEET) provides protection from biting arthropods but will not last through washing and will require more frequent reapplications.

Precautions when Using Insect Repellents

Travelers should take the following precautions:

  • Apply repellents only to exposed skin or clothing, as directed on the product label. Do not apply repellents under clothing.
  • Never use repellents over cuts, wounds, or irritated skin.
  • When using sprays, do not spray directly on face—spray on hands first and then apply to face. Do not apply repellents to eyes or mouth, and apply sparingly around ears.
  • Wash hands after application to avoid accidental exposure to eyes or ingestion.
  • Children should not handle repellents. Instead, adults should apply repellents to their own hands first, and then gently spread on the child’s exposed skin.
  • Avoid applying directly to children’s hands. After returning indoors, wash your child’s treated skin and clothing with soap and water or give the child a bath.
  • Use just enough repellent to cover exposed skin or clothing. Heavy application and saturation are generally unnecessary for effectiveness. If biting insects do not respond to a thin film of repellent, apply a bit more.
  • After returning indoors, wash repellent-treated skin with soap and water or bathe. Wash treated clothing before wearing it again. This precaution may vary with different repellents—check the product label.

If a traveler experiences a rash or other reaction, such as itching or swelling, from an insect repellent, the repellent should be washed off with mild soap and water and its use discontinued. If a severe reaction has occurred, a local poison-control center should be called for further guidance, if feasible. Travelers seeking health care because of the repellent should take the repellent to the doctor’s office and show the doctor. Permethrin should never be applied to skin but only to clothing, bed nets, or other fabrics as directed on the product label.

Children and Pregnant Women

Most repellents can be used on children aged >2 months. Protect infants aged <2 months from mosquitoes by using an infant carrier draped with mosquito netting with an elastic edge for a tight fit. Products containing OLE specify that they should not be used on children aged <3 years. Other than the safety tips listed above, EPA does not recommend any additional precautions for using registered repellents on children or on pregnant or lactating women.

Repellents and Sunscreen

Repellents that are applied according to label instructions may be used with sunscreen with no reduction in repellent activity; however, limited data show a one-third decrease in the sun protection factor (SPF) of sunscreens when DEET-containing insect repellents are used after a sunscreen is applied. Products that combine sunscreen and repellent are not recommended, because sunscreen may need to be reapplied more often and in larger amounts than needed for the repellent component to provide protection from biting insects. In general, the recommendation is to use separate products, applying sunscreen first and then applying the repellent. Due to the decrease in SPF when using a DEET-containing insect repellent after applying sunscreen, travelers may need to reapply the sunscreen more frequently.

Reduce mosquitoes around your home

Eliminate standing water, which mosquitoes need to breed. To keep your house and yard free of mosquito pools:

  • Unclog roof gutters.
  • Empty children’s wading pools at least once a week, and preferably more often.
  • Change water in birdbaths at least weekly.
  • Get rid of old tires in your yard.
  • Empty outdoor flower pots regularly or store them upside down so that they can’t collect water.
  • Drain your fire pit if water collects there.

Mosquito bites treatment

The main treatment aim of insect bites is to prevent itching.

Mosquito bite home remedy

  • Apply a cool compress. Try soothing the bite by applying a cold pack or a cool, moist cloth for a few minutes.
  • Apply topical calamine lotion or local anesthetic agent.
  • Take an oral antihistamine. For stronger reactions, try taking a nonprescription antihistamine (Benadryl, Chlor-Trimeton, others).
  • Use moderate potency topical steroids for papular urticaria or persistent reactions.

Putting calamine lotion or nonprescription hydrocortisone cream on the bite can help ease the itch. Or try dabbing the bite with a paste made of baking soda and water. Reapply several times daily until your symptoms go away.

Bites from insects carrying disease require specific antimicrobial therapy to treat the disease.

Management of mosquito bites may also include:

  • Topical steroid cream – this should be applied as soon as the itchy spots appear.
  • Antihistamine tablets – these may reduce the spots and reduce itching.
  • Antiseptic cream to reduce or avoid secondary infection.
  • Insecticides to rid the house, work place or school, of insects.
  • Wearing fully covering clothing.
  • Insect repellents applied to exposed skin to prevent mosquito bites and other insects when outdoors.

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