Typhoid

TYPHOID

Typhoid, or enteric, fever is a serious systemic disease caused by a bacillus, Salmonella typhi. Paratyphoid fever is closely related, though generally less severe. The enteric fevers have an incubation period of one to four weeks, followed by a slow onset and prolonged course, primarily affecting the gastrointestinal tract. There is a low fever and severe toxemia. A skin rash may occur in the early stages, and later other organs (liver, kidneys, bone marrow, brain) may be invaded. Typhoid is fatal in about 3 to 4 percent of cases, with higher proportions occurring where diagnostic and treatment facilities are inadequate. Diagnosis sometimes can be made clinically on the basis of patient history and physical examination, but usually depends on isolating the organism from feces or blood culture. Worldwide there are about 16 million cases annually, resulting in 600,000 deaths; in the United States there are usually less than 500 cases a year.

Typhoid is transmitted in feces—usually in polluted water, though sometimes in food that has been prepared under unhygienic conditions by a convalescent or chronic carrier. Humans are the only host for typhoid bacilli, but paratyphoid can be carried and transmitted by domestic animals. Cases continue to excrete the infective organisms in feces, and sometimes in urine, for varying periods, sometimes up to several months after apparent clinical recovery. A chronic (e.g., virtually permanent) carrier state occurs in a small number of cases; "Typhoid Mary" was a notorious example.

There may be other intermediaries between the human source and the victim who consumes contaminated water or food. For instance, water in a river estuary polluted with raw sewage containing typhoid bacilli may be ingested by shellfish or mussels, and these are then infective. It does not require a massive dose of viable typhoid bacilli to cause the disease. There are many well-documented cases of typhoid following ingestion of minuscule amounts of contaminated water or food. For instance, it suffices to eat a few lettuce leaves from a salad that was washed in contaminated water. For this reason, travelers to regions where typhoid is endemic must exercise extreme caution in what they eat and drink. All those who travel to places where typhoid occurs should also be offered prophylactic typhoid vaccine. In the past this has required several injections of vaccine, which often induced painful and sometimes unpleasantly toxic reactions. An oral vaccine is now available.

Cases of typhoid are treated with antibiotics, and notification to public health authorities is mandatory. It is rare in communities with efficient sanitary sewage disposal services and pure water supplies—the occurrence of even a single case indicates a breakdown of sanitation and hygiene in such communities, unless the disease was acquired elsewhere. A careful and complete epidemiological investigation of every case, including a detailed history of food and fluid intake, is therefore essential in order to identify the source of the infection so it can be controlled. Epidemics of typhoid rarely occur now, although they are always a potential threat when disasters such as earthquakes and floods disable sewage treatment plants. Until about the first quarter of the twentieth century, typhoid fever was endemic in all nations, and it caused the deaths of many famous people, including Albert, the consort of Queen Victoria;U.S. president Zachary Taylor; and English poet Rupert Brooke.

John M. Last

(see also: Food-Borne Diseases; Typhoid Mary; Waterborne Diseases )