Today, typhoid fever is rare in industrialized countries, although it remains a serious health threat in the developing world.
Typhoid fever spreads through contaminated food and water or through close contact with someone who's infected. Signs and symptoms usually include high fever, headache, abdominal pain and either constipation or diarrhea. People who are severely ill may experience delirium, shock and intestinal hemorrhage. A related condition, paratyphoid fever, causes similar problems, but in a milder form.
When treated with antibiotics, most people recover in a few weeks, although a small percentage - especially older adults and those with chronic diseases - die of complications of the disease. And a few people, like Mary Mallon, continue to carry the bacteria in their bodies and to infect others, even though they appear healthy.
Vaccines against typhoid fever are available, but they're only partially effective and are usually reserved for people who may be exposed to the disease or are traveling to areas where typhoid fever is endemic. No vaccine exists for paratyphoid fever.
Signs and symptoms
Although children with typhoid fever sometimes become sick quite suddenly, signs and symptoms are more likely to develop gradually — often appearing one to three weeks after you've been exposed to the disease. In some cases you may not become sick for as long as two months after exposure. The incubation period for paratyphoid fever is shorter — usually one to 10 days.
Once signs and symptoms do appear, you're likely to experience:
During the second week, you may develop a rash of small, flat, rose-colored spots on your lower chest or upper abdomen. The rash is temporary, usually disappearing in three or four days. If you don't receive treatment for typhoid fever, you may enter a second stage during which you become very ill. Your fever will remain high, and you may develop either diarrhea that has the color and consistency of pea soup or severe constipation. You may lose considerable weight during this phase, and your abdomen may become extremely distended.
By the third week, you may become delirious, lying motionless and exhausted with your eyes half-closed in what's known as the typhoid state. Life-threatening complications often develop at this time.
Improvement may come slowly during the fourth week. Your fever is likely to decrease gradually until your temperature returns to normal in another week to 10 days. But signs and symptoms can return up to two weeks after your fever has subsided. For reasons that aren't clear, you're more likely to have a relapse if you're treated with antibiotics early in the course of the disease.
Paratyphoid fever causes signs and symptoms similar to those of typhoid fever, but in a milder form. Complications aren't as severe, and you generally recover more quickly.
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 bacteria responsible for salmonellosis, another serious intestinal infection.
The 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.
Even 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.
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 ages 5 to 12 years are at greatest risk of contracting the disease, although they generally have milder symptoms and fewer complications than adults do. There's also increasing concern that the incidence of typhoid fever in children younger than 5 is greater than previously thought.
If you live in a country where typhoid and paratyphoid fevers are rare, you're at increased risk if you: