Typhoid fever

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Causes
Typhoid fever appears to have afflicted human beings for millennia, but the cause of the illness — a virulent and invasive bacterium called Salmonella typhi — wasn't discovered until the late 19th century. A different pathogen, Salmonella paratyphi, causes paratyphoid fever. Although they're related, these aren't the same as the bacteria responsible for salmonellosis, another serious intestinal infection.
Fecal-oral routeThe bacteria that cause typhoid and paratyphoid fever both spread through contaminated food or water and occasionally through direct contact with someone who is already infected. In developing nations, where typhoid and paratyphoid are endemic, most cases result from contaminated drinking water and poor sanitation. The majority of people in industrialized countries pick up the typhoid bacteria while traveling and spread it to others through the fecal-oral route.
This means that S. typhi and S. paratyphi are passed in the feces and sometimes in the urine of infected people. You can contract the infection if you eat food handled by someone with typhoid fever who hasn't washed carefully after using the bathroom. You can also become infected by drinking water contaminated with the bacteria.
Typhoid carriersEven after treatment with antibiotics, a small number of people who recover from typhoid fever continue to harbor the bacteria in their intestinal tract or gallbladder, often for years. These people, called chronic carriers, shed the bacteria in their feces and are capable of infecting others, although they no longer have signs or symptoms of the disease themselves.
Risk factors
Typhoid fever remains a serious threat in the developing world, where it affects more than 12 million people annually. The disease is endemic in India, Southeast Asia, Africa, South America and in certain regions of the former Soviet Union, especially Tajikistan and Uzbekistan.
Worldwide, children are at greatest risk of contracting the disease, although they generally have milder symptoms and fewer complications than adults do.
If you live in a country where typhoid and paratyphoid fevers are rare, you're at increased risk if you:
Work in or travel to areas where typhoid fever is endemic
Have close contact with someone who is infected or has recently been infected with typhoid fever
Have an immune system weakened by medications such as corticosteroids or diseases such as HIV/AIDS
Drink water contaminated by sewage that contains S. typhi
sks of complications and death increase. What's more, failure to treat an infection properly leads to longer periods in which a person is contagious and able to spread the resistant strain to others. And because bacteria mutate much more quickly than researchers can develop new antibiotics, the possibility exists that one day highly lethal strains of resistant bacteria will evolve and doctors will have no effective way to treat them.
In recent years, S. typhi has proved resistant to trimethoprim-sulfamethoxazole, ampicillin and tetracycline, in addition to chloramphenicol. In some parts of the world, such as Vietnam and Tajikistan, resistance has begun to extend even to new antibiotics such as ciprofloxacin (Cipro).
In the United States, most doctors now prescribe ciprofloxacin for adults other than pregnant women. Women who are pregnant and children most often receive ceftriaxone (Rocephin) injections. Still, all of these drugs can cause side effects and long-term use can lead to the development of antibiotic-resistant strains of bacteria.
Other treatment steps aimed at managing symptoms include:
Drinking fluids. This helps prevent the dehydration that results from a prolonged fever and diarrhea. If you're severely dehydrated, you may need to receive fluids through a vein in your arm (intravenously).
Eating a healthy diet. Nonbulky, high-calorie meals can help replace the nutrients you lose when you're sick.


Prevention
In many developing nations, the public health goals that can help prevent and control typhoid — safe drinking water, improved sanitation and adequate medical care — may be difficult to achieve. For that reason, some experts believe that vaccinating high-risk populations is the best way to control typhoid fever.
Two vaccines are currently in use — one is injected in a single dose, and the other is administered orally over a period of days. Neither is 100 percent effective, and both require repeat vaccinations. No vaccine exists for paratyphoid fever.
If you're traveling to an area where typhoid fever is endemic, consider being vaccinated. But because the vaccine won't provide complete protection, be sure to follow these guidelines as well:
Wash your hands. Frequent hand washing is the best way to control infection. Wash your hands thoroughly with hot, soapy water, especially before eating or preparing food and after using the toilet. Carry an alcohol-based hand rub for times when water isn't available.
Avoid untreated water. Contaminated drinking water is a particular problem in areas where typhoid is endemic. For that reason, drink only bottled water or canned or bottled carbonated beverages, wine and beer. Carbonated bottled water is safer than still water is. Wipe the outside of all bottles and cans before you open them. Ask for drinks without ice. Use bottled water to brush your teeth, and try not to swallow water in the shower.
Avoid raw fruits and vegetables. Because raw produce may have been washed in unsafe water, avoid fruits and vegetables that you can't peel, especially lettuce. To be absolutely safe, you may want to avoid raw foods entirely.
Choose hot foods. Avoid food that's stored or served at room temperature. Steaming hot foods are best. And although there's no guarantee that meals served at the finest restaurants are safe, it's best to avoid food from street vendors — it's more likely to be contaminated.
To prevent infecting othersIf you're recovering from typhoid or paratyphoid, these measures can help keep others safe:
Wash your hands often. This is the single most important thing you can do to keep from spreading the infection to others. Use plenty of hot, soapy water and scrub thoroughly for at least 30 seconds, especially before eating and after using the toilet.
Clean household items daily. Clean toilets, door handles, telephone receivers and taps at least once a day with a household cleaner and paper towels or disposable cloths.
Avoid handling food. Avoid preparing food for others until your doctor says you're no longer contagious. If you work in the food service industry or a health care facility, you won't be allowed to return to work until tests show that you're no longer shedding typhoid bacteria.
Keep personal items separate. Set aside towels, bed linen and utensils for your own use and wash them frequently in hot, soapy water. Heavily soiled items can be soaked first in disinfectant.


Screening and diagnosis
Your doctor is likely to suspect typhoid or paratyphoid fever based on your symptoms and your medical and travel history. But the diagnosis is usually confirmed by identifying S. typhi or S. paratyphi in a culture of your blood or other body fluid or tissue.
For the culture, a small sample of your blood, stool, urine or bone marrow is placed on a special medium that encourages the growth of bacteria. In 48 to 72 hours, the culture is checked under a microscope for the presence of typhoid bacteria. A bone marrow culture often is the most sensitive test for S. typhi.
Your doctor may recommend other tests to help diagnose typhoid fever, such as:
Enzyme-linked immunosorbent assay (ELISA). This blood test looks for an antigen that's specific to typhoid bacteria. An antigen is any substance, such as a virus, bacterium, toxin or foreign protein, that triggers an immune system response in your body.
Fluorescent antibody test. This test checks for antibodies to S. typhi. Antibodies are proteins produced by your immune system in response to harmful substances (antigens). Each antibody is unique and defends your body against a single antigen.