What is salmonella

Salmonella is a bacteria that can cause food poisoning or salmonellosis (Salmonella enterocolitis), which is an infection of the lining of the small intestine. Salmonella infection is a type of gastroenteritis (or ‘gastro’). Salmonella was discovered by an American scientist named Dr. Salmon, and has been known to cause illness for over 125 years. Salmonella poisoning symptoms include diarrhea, stomach cramps and sometimes vomiting and fever. The most common serotypes of Salmonella that cause human infection are Salmonella Enteritidis, Salmonella Typhimurium, Salmonella Newport, and Salmonella Javiana. These Salmonella serotypes account for about half of culture-confirmed Salmonella isolates reported by public health laboratories ¹.

Most people infected with Salmonella develop diarrhea, fever, and abdominal cramps between 12 and 72 hours after infection. The illness usually lasts 4 to 7 days, and most individuals recover without treatment. In some cases, diarrhea may be so severe that the patient needs to be hospitalized. In these patients, the Salmonella infection may spread from the intestines to the blood stream, and then to other body sites. In these cases, Salmonella can cause death unless the person is treated promptly with antibiotics. The elderly, infants, and those with impaired immune systems are more likely to have a severe illness1.

Anyone can get salmonella, but young children, the elderly and people who have immune systems that are not working properly (including people with cancer, AIDS or alcoholism) have a greater risk of becoming severely ill. Children under the age of 5 are at the highest risk for Salmonella infection than any other age group ¹.

The Centers for Disease Control and Prevention ² estimates that approximately 1.2 million illnesses and approximately 450 deaths occur due to non-typhoidal Salmonella annually in the United States.

There are many different kinds of Salmonella bacteria. Salmonella serotype Typhimurium and Salmonella serotype Enteritidi are the most common in the United States ¹. Salmonella infections are more common in the summer than winter.

Salmonella incubation period

On average, it takes from 12 to 72 hours for the symptoms to develop after swallowing an infectious dose of salmonella.

How long does salmonella last

Symptoms usually last for four to seven days and most people recover without treatment.

But if you become seriously ill, you may need hospital care because the dehydration caused by the salmonella bacteria can be life-threatening.

How do you get salmonella

You usually get salmonella by eating contaminated food. Salmonella bacteria live in the gut of many farm animals and can affect meat, eggs, poultry and milk. Other foods like green vegetables, fruit and shellfish can become contaminated through contact with manure in the soil or sewage in the water.

Contamination is also possible if raw and cooked foods are stored together. Most tortoises and terrapins and other pet reptiles can also carry salmonella. Dogs, cats and rodents can occasionally become infected.

It is impossible to tell from its appearance whether food is contaminated with salmonella. It will look, smell and taste normal.

Salmonella can be spread from person to person by poor hygiene, by failing to wash your hands properly after going to the toilet, or after handling contaminated food.

Salmonella prevention

There is no vaccine to prevent salmonellosis. Because foods of animal origin may be contaminated with Salmonella, people should not eat raw or undercooked eggs, poultry, or meat. Raw eggs may be unrecognized in some foods, such as homemade Hollandaise sauce, Caesar and other homemade salad dressings, tiramisu, homemade ice cream, homemade mayonnaise, cookie dough, and frostings. Poultry and meat, including hamburgers, should be well-cooked, not pink in the middle. Persons also should not consume raw or unpasteurized milk or other dairy products. Produce should be thoroughly washed.

Cross-contamination of foods should be avoided. Uncooked meats should be kept separate from produce, cooked foods, and ready-to-eat foods. Hands, cutting boards, counters, knives, and other utensils should be washed thoroughly after touching uncooked foods. Hand should be washed before handling food, and between handling different food items.

People who have salmonellosis should not prepare food or pour water for others until their diarrhea has resolved. Many health departments require that restaurant workers with Salmonella infection have a stool test showing that they are no longer carrying the Salmonella bacterium before they return to work.

People should wash their hands after contact with animal feces. Because reptiles are particularly likely to have Salmonella, and it can contaminate their skin, everyone should immediately wash their hands after handling reptiles. Reptiles (including turtles) are not appropriate pets for small children and should not be in the same house as an infant. Salmonella carried in the intestines of chicks and ducklings contaminates their environment and the entire surface of the animal. Children can be exposed to the bacteria by simply holding, cuddling, or kissing the birds. Children should not handle baby chicks or other young birds. Everyone should immediately wash their hands after touching birds, including baby chicks and ducklings, or their environment.

Some prevention steps occur everyday without you thinking about it. Pasteurization of milk and treatment of municipal water supplies are highly effective prevention measures that have been in place for decades. In the 1970s, small pet turtles were a common source of salmonellosis in the United States, so in 1975, the sale of small turtles was banned in this country. However, in 2008, they were still being sold, and cases of Salmonella associated with pet turtles have been reported. Improvements in farm animal hygiene, in slaughter plant practices, and in vegetable and fruit harvesting and packing operations may help prevent salmonellosis caused by contaminated foods. Better education of food industry workers in basic food safety and restaurant inspection procedures may prevent cross-contamination and other food handling errors that can lead to outbreaks. Wider use of pasteurized egg in restaurants, hospitals, and nursing homes is an important prevention measure. In the future, irradiation or other treatments may greatly reduce contamination of raw meat.

Wash your hands thoroughly with soap and warm water:

• before preparing and eating food
• after handling raw food
• after going to the toilet or changing a baby’s nappy
• after contact with pets and other animals, especially reptiles and amphibians
• after working in the garden

Also:

• Keep cooked food away from raw food
• Store raw foods below cooked or ready-to-eat foods in the fridge to prevent contamination
• Wash raw fruits and vegetables thoroughly before eating
• Cook poultry, ground beef, and eggs thoroughly. Cook food thoroughly, especially meat, so that it is piping hot
• Do not eat or drink foods containing raw eggs, or raw (unpasteurized) milk.
• If you are served undercooked meat, poultry or eggs in a restaurant, don’t hesitate to send it back to the kitchen for further cooking.
• Wash hands, kitchen work surfaces, and utensils with soap and water immediately after they have been in contact with raw meat or poultry.
• Be particularly careful with foods prepared for infants, the elderly, and the immunocompromised.Wash hands with soap after handling reptiles, birds, or baby chicks, and after contact with pet feces.
• Avoid direct or even indirect contact between reptiles (turtles, iguanas, other lizards, snakes) and infants or immunocompromised persons.Don’t work with raw poultry or meat, and an infant (e.g., feed, change diaper) at the same time.
• Mother’s milk is the safest food for young infants. Breastfeeding prevents salmonellosis and many other health problems.
• Keep all kitchen surfaces and equipment including knives, chopping boards and dish cloths clean
• Do not drink untreated water from lakes, rivers or streams
• Do not keep reptiles or amphibians in households where there is a child under 5 year of age, or someone with a weakened immune system

If someone has salmonella, wash all dirty clothes, bedding and towels in the washing machine on the hottest cycle possible.

Clean toilet seats, toilet bowls, flush handles, taps and wash hand basins after use with detergent and hot water, followed by a household disinfectant.

Is salmonella contagious?

Yes. While you are ill and have symptoms, you are infectious. Children and adults should stay away from nursery, school or work for 48 hours after the symptoms have stopped.

If you have salmonella you should avoid contact with other people for at least 24 hours after your vomiting and diarrhea stops. You should tell your employer you have had salmonella if you work with vulnerable groups such as the elderly, the young or those in poor health, or if you handle food.

Salmonella causes

Salmonella live in the intestinal tracts of humans and animals. You can get Salmonella infection from a variety of sources, including:

• Eating contaminated food or drinking contaminated water.
• Touching infected animals and not washing your hands afterwards.

Contaminated Food or Water

Salmonella is usually transmitted to humans by eating foods contaminated with small amounts of animal feces. Contaminated foods usually look and smell normal. They are often foods of animal origin, such as beef, poultry, milk, fish, or eggs, but any food, including vegetables and fruit or processed foods, may become contaminated.

Foods can also be contaminated in the kitchen. Drippings from raw meat or poultry can contaminate surfaces and other foods in the refrigerator or shopping cart. When raw meat or poultry are prepared with a cutting board and knife without being washed thoroughly between uses, they can contaminate other foods.

When preparing raw meat or poultry, food handlers can transfer Salmonella on their hands to other foods if they do not wash their hands between food preparation steps. Food handlers who do not wash their hands with soap after using the bathroom can also contaminate food with Salmonella.

Contact with Infected Animals

Salmonella live in the intestinal tracts of humans and other animals, including poultry and other birds, amphibians, and reptiles. Salmonella may be found in the feces of some animals, and people can become infected if they do not wash their hands after contact with animals or animal feces.

Many animals can carry Salmonella germs but appear perfectly healthy and clean. Animals’ bodies, whether covered with fur, feathers, or scales, can be contaminated with germs. Reptiles, such as turtles, lizards, and snakes, are particularly likely to harbor Salmonella. Many chicks, ducks, and other poultry including those in backyard flocks can carry Salmonella in their feces. You cannot look at an animal and tell if it is infected with Salmonella.

The area where an animal lives, such as its cage or water in its tank or the places where an animal roams, may be contaminated with Salmonella, which can cause illness in people who come into direct contact with the animal area, cage, or tank water.

Risk Factors for Salmonella infection

• Salmonella infection is more common in the summer months (June, July, and August) than winter.
• Children under 5 years old are the most likely to get a Salmonella infection ³.
• Infants who are not breast fed are more likely to get a Salmonella infection ⁴.
• Children who are 5 years old and younger, adults over 65 years old, and people with weakened immune systems are the most likely to have severe infections.
• Certain medications (for example, medications to reduce stomach acid) can increase the risk of Salmonella infection ⁵.

Salmonella signs and symptoms

Salmonellosis, the illness caused by Salmonella, primarily results in a mild to severe diarrheal illness, known as acute gastroenteritis.

Symptoms of acute gastroenteritis due to infection with Salmonella can include ⁶:

• Sudden onset of diarrhea (which may be bloody or mucus in stools)
• Abdominal cramps
• Fever (almost always present)
• Nausea, vomiting, and headache may occur, though less frequent
• Loss of appetite

Diarrhea may last for several days and lead to potentially severe dehydration, especially in infants and children under 2 years old and in adults over 65 years old. Even after clinical symptoms are no longer obvious, Salmonella bacteria may be found in the stool for several weeks.

Most people with diarrhea due to a Salmonella infection recover completely, although it may be several months before their bowel habits are entirely normal.

Sometimes, Salmonella infection can spread to urine, blood, bones, joints, the brain, or the nervous system, causing symptoms related to that body part or system. Some of these extra-intestinal infections can have long-term effects, depending on which part of the body is infected.

Invasive Salmonella Infections

When Salmonella infections become invasive, they can affect the bloodstream, bone, joint, brain, or nervous system, or other internal organs.

Invasive Salmonella infections:

• Can be severe and potentially life-threatening.
• Occur in about 8 percent of persons with laboratory-confirmed Salmonella infection.10
• May occur as:
  • Bacteremia (infection of the blood)
  • Meningitis (infection of the membranes lining the brain and spinal cord)
  • Osteomyelitis (infection of the bone)
  • Septic arthritis (infection of a joint).
• Are rarely fatal, but most commonly occur in people who are very young or old or have a weakened immune system.

Salmonella diagnosis

Diagnosing salmonellosis requires testing a clinical specimen (such as stool or blood) from an infected person to distinguish it from other illnesses that can cause diarrhea, fever, and abdominal cramps. Once Salmonella is identified in the specimen, additional testing can be done to further characterize the Salmonella.

Steps in Laboratory Testing and Reporting Salmonella

• Laboratory scientists identify Salmonella infection by culturing a patient’s sample. If Salmonella bacteria grow, then the diagnosis is confirmed, or in laboratory-terms, “culture confirmed.”
• Clinical diagnostic laboratories report the test results to the treating clinician and submit Salmonella isolates to state and territorial public health laboratories for serotyping and DNA fingerprinting.
• The public health laboratories report the results to Centers for Disease Control and Prevention’s Laboratory-based Enteric Disease Surveillance
• The public health laboratories forward atypical serotypes to Centers for Disease Control and Prevention’s National Salmonella Reference Laboratory for more characterization or confirmation.

Salmonella treatment

Salmonella gastrointestinal infections usually resolve, or get better, in 5-7 days. Most do not require treatment other than oral fluids. People with severe diarrhea may require rehydration with intravenous fluids.

• It is important to drink plenty of fluids as diarrhea or vomiting can lead to dehydration and you can lose important sugars and minerals from your body. Your doctor may recommend a rehydration solution, available from your pharmacist.

Sometimes severe cases are treated with antibiotics. If you are given antibiotics, it is essential that you complete the course as prescribed. Choices for antibiotic therapy for severe infections often include fluoroquinolones, third-generation cephalosporins, or ampicillin.

Antibiotics are recommended only for patients who:

• Have a serious illness (such as severe diarrhea, high fever, bloodstream infection, or condition requiring hospitalization).
• Are considered at high risk for serious disease or complications (such as infants, adults over 65 years old, and people with weakened immune systems).

Some Salmonella bacteria are resistant to antibiotics. Sometimes the bacteria that cause infections are resistant to the drug of choice, and this drug doesn’t work. Physicians must then recommend second- or third-choice drugs for treatment, but these drugs might be less effective, more toxic, or more expensive.

Resistance to antimicrobial agents is not uncommon in Salmonella. Data from the National Antimicrobial Resistance Monitoring System show that 5% of non-typhoidal Salmonella are resistant to five or more antimicrobial agents ⁷.

Are there long-term consequences to a Salmonella Infection?

People with diarrhea due to a Salmonella infection usually recover completely, although it may be several months before their bowel habits are entirely normal.

A small number of people with Salmonella develop pain in their joints. This is called reactive arthritis. Reactive arthritis can last for months or years and can lead to chronic arthritis, which can be difficult to treat1. Antibiotic treatment of the initial Salmonella infection does not make a difference in whether or not the person develops arthritis ⁸. People with reactive arthritis can also develop irritation of the eyes and painful urination ⁹.

Salmonella bacteria serotypes

Serotypes are groups within a single species of microorganisms, such as bacteria or viruses, which share distinctive surface structures. For instance, Salmonella bacteria look alike under the microscope but can be separated into many serotypes based on two structures on their surface:

• The outermost portion of the bacteria’s surface covering, called the O antigen. The bacteria’s surface are covered with lipopolysaccharide. The outermost portion of the lipopolysaccharide is the O antigen.
• A slender threadlike structure, called the H antigen, that is part of the flagella. Flagella are whip-like tails that bacteria use to move around. Flagella is the whole structure, while the slender threadlike portion of the flagella is called the H antigen.

The O antigens are distinguished by their different chemical make-up. The H antigens are distinguished by the protein content of the flagella. Each O and H antigen has a unique code number. Scientists determine the serotype based on the distinct combination of O and H antigens.

Figure 1. Salmonella bacteria

Different Serotypes

Salmonella have many different serotypes. Some serotypes are only found in one kind of animal or in a single place. Others are found in many different animals and all over the world. Some can cause especially severe illnesses when they infect people; while others cause milder illnesses.

More than 2,500 serotypes have been described for Salmonella; but, because they are rare, scientists know very little about most of them. Less than 100 serotypes account for most human infections. What scientists learn about the more common serotypes can help us better understand illness and the natural history of all the Salmonella strains.

Some groups of people, such as older adults, people with weakened immune systems, and children under five years old have a higher risk for Salmonella infection. Infections in these groups can be more severe, resulting in long-term health consequences or death.

Serotypes and Outbreaks

Since the 1960s, public health scientists in the US have used serotyping to help find Salmonella outbreaks and track them to their sources. Laboratory experts serotype the Salmonella from infected people. When cases with one serotype increase, they suspect an outbreak and disease detectives start their investigation .

Serotyping has been the core of public health monitoring of Salmonella infections for over 50 years. Now, scientists use DNA testing to further divide each serotype into more subtypes and to detect more outbreaks. With the next generation of sequencing technology, advancements continue as the laboratory can find information about the species, serovar, and subtype of bacteria in just one test. Currently, at least two scientists must generate these three important pieces of information using three separate tests or more.

How do serotyping and serology differ?

Serotyping is a subtyping test based on differences in microbial (e.g., viral or bacterial) surfaces. Serology refers to the antibodies that form because of a viral or bacterial infection. Serotyping is sometimes referred to as serology, but this is technically inaccurate.

Salmonella and Antibiotic Resistance

Resistance to two clinically important drugs, ceftriaxone (a cephem) and ciprofloxacin (a quinolone), has climbed in non-typhoidal Salmonella since 1996. In 2011, about 5% of Salmonella tested by CDC were resistant to five or more types of drugs.

Typhoidal and Nontyphoidal Salmonella

Salmonella bacteria are classified as either “typhoidal” or “nontyphoidal,” based on their serotype.

• Typhoidal Salmonella refers to the specific Salmonella serotypes which cause typhoid fever or paratyphoid fever, including Typhi, Paratyphi A, Paratyphi B (see note below), and Paratyphi C. Serotype Paratyphi B is tartrate-negative (unable to ferment tartrate) and causes typhoidal disease.
  • Serotype Paratyphi B var. L(+)tartrate+ is tartrate-positive (able to ferment tartrate) and causes nontyphoidal disease.
• Nontyphoidal Salmonella refers to all other Salmonella serotypes ¹⁰.

Salmonella typhi

Typhoid fever is a life-threatening illness caused by the bacterium Salmonella Typhi. An estimated 5,700 cases occur each year in the United States. Most cases (up to 75%) are acquired while traveling internationally. Typhoid fever is still common in the developing world, where it affects about 21.5 million people each year.

The incubation period of typhoid and paratyphoid infections is 6–30 days. The onset of illness is insidious, with gradually increasing fatigue and a fever that increases daily from low-grade to as high as 102°F–104°F (38°C–40°C) by the third to fourth day of illness. Headache, malaise, and anorexia are nearly universal, and abdominal pain, diarrhea, or constipation are common. Hepatosplenomegaly can often be detected. A transient, macular rash of rose-colored spots can occasionally be seen on the trunk. Fever is commonly lowest in the morning, reaching a peak in late afternoon or evening. This clinical presentation is often confused with malaria, and typhoid fever should be suspected in a person with a history of travel to an endemic area who is not responding to antimalarial medication. Untreated, the disease can last for a month. The serious complications of typhoid fever generally occur after 2–3 weeks of illness and may include life-threatening intestinal hemorrhage or perforation.

Without therapy, the illness may last for 3 to 4 weeks and death rates range between 12% and 30%.

Typhoid (typhoid fever) causes a high fever, fatigue, weakness, stomach pains, headache, loss of appetite, and sometimes a rash. If it is not treated, it can kill up to 30% of people who get it. Some people who get typhoid become “carriers,” who can spread the disease to others. Generally, people get typhoid from contaminated food or water. Typhoid is rare in the U.S., and most U.S. citizens who get the disease get it while traveling.

Typhoid fever can be prevented and can usually be treated with antibiotics. Typhoid vaccine can prevent typhoid. There are two vaccines to prevent typhoid. One is an inactivated (killed) vaccine gotten as a shot. The other is a live, attenuated (weakened) vaccine which is taken orally (by mouth). If you are planning to travel outside the United States, you should know about typhoid fever and what steps you can take to protect yourself.

How is typhoid fever spread?

Salmonella Typhi lives only in humans. Persons with typhoid fever carry the bacteria in their bloodstream and intestinal tract. In addition, a small number of persons, called carriers, recover from typhoid fever but continue to carry the bacteria. Both ill persons and carriers shed Salmonella Typhi in their feces (stool).

You can get typhoid fever if you eat food or drink beverages that have been handled by a person who is shedding Salmonella Typhi or if sewage contaminated with Salmonella Typhi bacteria gets into the water you use for drinking or washing food. Therefore, typhoid fever is more common in areas of the world where handwashing is less frequent and water is likely to be contaminated with sewage.

Once Salmonella Typhi bacteria are eaten or drunk, they multiply and spread into the bloodstream. The body reacts with fever and other signs and symptoms.

Where in the world do you get typhoid fever?

Typhoid fever is common in most parts of the world except in industrialized regions such as the United States, Canada, western Europe, Australia, and Japan. Therefore, if you are traveling to the developing world, you should consider taking precautions. Other areas of risk include East and Southeast Asia, Africa, the Caribbean, and Central and South America. The most recent pre-travel vaccination guidelines can be found at https://wwwnc.cdc.gov/travel.

How can you avoid typhoid fever?

Two basic actions can protect you from typhoid fever:

• Avoid risky foods and drinks.
• Get vaccinated against typhoid fever.

It may surprise you, but watching what you eat and drink when you travel is as important as being vaccinated. This is because the vaccines are not completely effective. Avoiding risky foods will also help protect you from other illnesses, including travelers’ diarrhea, cholera, dysentery, and hepatitis A.

“Boil it, cook it, peel it, or forget it”

• If you drink water, buy it bottled or bring it to a rolling boil for 1 minute before you drink it. Bottled carbonated water is safer than uncarbonated water.
• Ask for drinks without ice unless the ice is made from bottled or boiled water. Avoid popsicles and flavored ices that may have been made with contaminated water.
• Eat foods that have been thoroughly cooked and that are still hot and steaming.
• Avoid raw vegetables and fruits that cannot be peeled. Vegetables like lettuce are easily contaminated and are very hard to wash well.
• When you eat raw fruit or vegetables that can be peeled, peel them yourself. (Wash your hands with soap first.) Do not eat the peelings.
• Avoid foods and beverages from street vendors. It is difficult for food to be kept clean on the street, and many travelers get sick from food bought from street vendors.

Who should get typhoid vaccine and when?

Routine typhoid vaccination is not recommended in the United States, but typhoid vaccine is recommended for:

• Travelers to parts of the world where typhoid is common. (NOTE: typhoid vaccine is not 100% effective and is not a substitute for being careful about what you eat or drink).
• People in close contact with a typhoid carrier.
• Laboratory workers who work with Salmonella Typhi bacteria.

Inactivated typhoid vaccine (shot)

• One dose provides protection. It should be given at least 2 weeks before travel to allow the vaccine time to work.
• A booster dose is needed every 2 years for people who remain at risk.

Live typhoid vaccine (oral)

Four doses: one capsule every other day for a week (day 1, day 3, day 5, and day 7). The last dose should be given at least 1 week before travel to allow the vaccine time to work.

• Swallow each dose about an hour before a meal with a cold or lukewarm drink. Do not chew the capsule.
• A booster dose is needed every 5 years for people who remain at risk.

Either vaccine may safely be given at the same time as other vaccines.

Some people should not get typhoid vaccine or should wait

Inactivated typhoid vaccine (shot)

• Should not be given to children younger than 2 years of age.
• Anyone who has had a severe reaction to a previous dose of this vaccine should not get another dose.
• Anyone who has a severe allergy to any component of this vaccine should not get it. Tell your doctor if you have any severe allergies.
• Anyone who is moderately or severely ill at the time the shot is scheduled should usually wait until they recover before getting the vaccine.

Live typhoid vaccine (oral)

• Should not be given to children younger than 6 years of age.
• Anyone who has had a severe reaction to a previous dose of this vaccine should not get another dose.
• Anyone who has a severe allergy to any component of this vaccine should not get it. Tell your doctor if you have any severe allergies.
• Anyone who is moderately or severely ill at the time the vaccine is scheduled should usually wait until they recover before getting it. Tell your doctor if you have an illness involving vomiting or diarrhea.
• Anyone whose immune system is weakened should not get this vaccine. They should get the typhoid shot instead. This includes anyone who:
  – has HIV/AIDS or another disease that affects the immune system,
  – is being treated with drugs that affect the immune system, such as steroids for 2 weeks or longer,
  – has any kind of cancer,
  – is taking cancer treatment with radiation or drugs.
• Oral typhoid vaccine should not be given until at least 3 days after taking certain antibiotics.

Ask your doctor for more information.

Table 1. Vaccines to prevent typhoid fever

What are the risks from typhoid vaccine?

Like any medicine, a vaccine could cause a serious problem, such as a severe allergic reaction. The risk of typhoid vaccine causing serious harm, or death, is extremely small. Serious problems from either typhoid vaccine are very rare.

Inactivated typhoid vaccine (shot)

Mild reactions

• Fever (up to about 1 person in 100)
• Headache (up to about 1 person in 30)
• Redness or swelling at the site of the injection (up to about 1 person in 15)

Live typhoid vaccine (oral)

• Mild reactions
• Fever or headache (up to about 1 person in 20)
• Stomach pain, nausea, vomiting, rash (rare).

What are the signs and symptoms of typhoid fever?

Persons with typhoid fever usually have a sustained fever as high as 103° to 104° F (39° to 40° C). They may also feel weak, or have stomach pains, headache, or loss of appetite. In some cases, patients have a rash of flat, rose-colored spots. The only way to know for sure if an illness is typhoid fever is to have samples of stool or blood tested for the presence of Salmonella Typhi.

Typhoid or paratyphoid fever diagnosis

Infection with typhoid or paratyphoid fever results in a low-grade septicemia. Although blood culture is the mainstay of diagnosis in typhoid and paratyphoid fever, a single culture is positive in only approximately 50% of cases. Multiple cultures increase the sensitivity and may be required to make the diagnosis. Bone marrow culture increases the diagnostic yield to approximately 80% of cases and is relatively unaffected by prior or concurrent antibiotic use. Stool culture is not usually positive during the first week of illness, so blood culture is preferred. Urine culture has no higher diagnostic yield than stool culture for acute cases.

The Widal test is unreliable but is widely used in developing countries because of its low cost. It is a serologic assay that may react in patients with typhoid or paratyphoid fever, but is not specific and false positives may occur. Serologic assays are not an adequate substitute for blood, stool, or bone marrow culture.

Because there is no definitive serologic test for typhoid or paratyphoid fever, the initial diagnosis often has to be made clinically. The combination of a history of risk for infection and a gradual onset of fever that increases in severity over several days should raise suspicion of typhoid or paratyphoid fever. Typhoid fever is a nationally notifiable disease.

Typhoid or paratyphoid fever treatment

Typhoid fever is treated with antibiotics. Specific antimicrobial therapy shortens the clinical course of enteric fever and reduces the risk for death. Fluoroquinolones are recommended for empiric treatment of enteric fever in adults, but quinolone resistance is >80% for Typhi and Paratyphi A infections in travelers to South and Southeast Asia, which suggests that treatment failures will occur. Injectable third-generation cephalosporins are often the empiric drug of choice when the possibility of fluoroquinolone resistance is high. Azithromycin and ceftriaxone are increasingly used to treat typhoid fever or paratyphoid fever because of the emergence of multidrug-resistant strains, although increasing resistance to azithromycin in Typhi strains has been documented outside the United States. In contrast, no cases of ceftriaxone resistance have been reported among Typhi and Paratyphi A isolates tested by the CDC National Antimicrobial Monitoring System through 2013.

Patients treated with an antibiotic may continue to have fever for 3–5 days, although the height of the fever generally decreases each day. Patients may actually feel worse during the several days it takes for the fever to end. If fever in a person with culture-confirmed typhoid or paratyphoid fever does not subside within 5 days, alternative antimicrobial agents or other foci of infection such as abscesses, bone or joint infections, and other extraintestinal sites should be considered.

Typhoid fever’s danger doesn’t end when symptoms disappear

Even if your symptoms seem to go away, you may still be carrying Salmonella Typhi. If so, the illness could return, or you could pass the disease to other people. In fact, if you work at a job where you handle food or care for small children, you may be barred legally from going back to work until a doctor has determined that you no longer carry any typhoid bacteria.

If you are being treated for typhoid fever, it is important to do the following:

• Keep taking the prescribed antibiotics for as long as the doctor has asked you to take them.
• Wash your hands carefully with soap and water after using the bathroom, and do not prepare or serve food for other people. This will lower the chance that you will pass the infection on to someone else.
• Have your doctor perform a series of stool cultures to ensure that no Salmonella Typhi bacteria remain in your body.

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