typhoid fever, also called typhoid, acute infectious disease caused by a specific serotype of the bacterium Salmonella typhi. The bacterium usually enters the body through the mouth by the ingestion of contaminated food or water, penetrates the intestinal wall, and multiplies in lymphoid tissue; it first enters into the bloodstream within 24 to 72 hours, causing septicemia (blood poisoning) and systemic infection.
After an average 10–14-day incubation period, the early symptoms of typhoid appear: headache, malaise, generalized aching, fever, and restlessness that may interfere with sleep. There may be loss of appetite, nosebleeds, cough, and diarrhea or constipation. Persistent fever develops and gradually rises, usually in a stepwise fashion, reaching a peak of 39 or 40 °C (103 or 104 °F) after 7–10 days and continuing with only slight morning remissions for another 10–14 days.
During about the second week of fever, when typhoid bacilli are present in great numbers in the bloodstream, a rash of small, rose-coloured spots appears on the trunk, lasts four or five days, and then fades away. The lymph follicles (Peyer patches) along the intestinal wall in which the typhoid bacilli have multiplied become inflamed and necrotic and may slough off, leaving ulcers in the walls of the intestine. The dead fragments of intestinal tissue may erode blood vessels, causing hemorrhage, or they may perforate the intestinal wall, allowing the intestine’s contents to enter the peritoneal cavity (peritonitis). Other complications can include acute inflammation of the gallbladder, heart failure, pneumonia, osteomyelitis, encephalitis, and meningitis. With a continued high fever the symptoms usually increase in intensity, and mental confusion and delirium may appear.
By the end of the third week the patient is emaciated, abdominal symptoms are marked, and mental disturbance is prominent. In favourable cases, during about the beginning of the fourth week, the fever begins to decline, the symptoms begin to abate, and the temperature gradually returns to normal. If untreated, typhoid fever proves fatal in up to 25 percent of all cases. Patients with such diseases as cancer or sickle cell anemia are particularly prone to develop serious and prolonged infection with Salmonella.
Most major epidemics of typhoid fever have been caused by the pollution of public water supplies. Food and milk may be contaminated, however, by a carrier of the disease who is employed in handling and processing them; by flies; or by the use of polluted water for cleaning purposes. Shellfish, particularly oysters, grown in polluted water and fresh vegetables grown on soil fertilized or contaminated by untreated sewage are possible causes. The prevention of typhoid fever depends mainly on proper sewage treatment, filtration and chlorination of water, and the exclusion of carriers from employment in food industries and restaurants. In the early part of the 20th century, prophylactic vaccination using killed typhoid organisms was introduced, mainly in military forces and institutions, and contributed to a lowering of the incidence of the disease.
Diagnosis of typhoid fever is made by blood culture, stool culture, and serological testing. The treatment of typhoid fever is with antibiotics, particularly chloramphenicol. Chloramphenicol begins to lower the patient’s fever within three or four days after beginning therapy, and there is progressive improvement thereafter. The drug treatment is continued for several weeks in order to prevent relapses.
Typhoid bacteria can persist in the bile passages of patients for an indefinite period of time. These carriers can pass the infection to healthy persons if they practice poor hygiene or if they are food handlers. About 30 percent of persons infected with typhoid fever become transient carriers of the disease, excreting the causative bacteria in the stool or urine for weeks or months. About 5 percent remain long-term carriers, harbouring the microorganisms and shedding them for years. One of the most famous instances of carrier-borne disease in medical history was the case of “Typhoid Mary” (byname of Mary Mallon). Fifty-one original cases of typhoid and three deaths were directly attributed to her during the early 20th century.