Typhoid fever is more common in the tropics. It tends to occur in places where the sanitation standards are poor. Typhoid fever is caused by a bacterial organism called salmonella typhi. Salmonella paratyphi can also cause fever and abdominal symptoms. The disease caused by both these entities is called enteric fever. The disease presents with a typical, continuous fever for about three to four weeks, relative bradycardia with abdominal pain (due to enlargement of lymph nodes in the abdomen), and constipation.

Geographical distribution
Worldwide, typhoid fever affects about six million people with more than 6,00,000 deaths a year. Almost 80% of cases and deaths occur in Asia, and most others in Africa and Latin America. Among Asian countries, India probably has a large number of these cases.

Indian statistics
Typhoid fever is endemic in India. Health surveys conducted by the Central Ministry of Health in the community development areas indicated a morbidity rate varying from 102 to 2219 per 1,00,000 population in different parts of the country. A limited study in an urban slum showed 1% of children up to 17 years of age suffer from typhoid fever every year.

Carriers of typhoid fever
Typhoid infection is mainly acquired from persons who are carriers of the disease. Carriers are people who continue to excrete salmonella through their urine and feces a year after an attack of typhoid. A chronic carrier state develops in about 2 to 5% of the cases. The organisms in such cases make the gall bladder their habitat.