Typhoid fever: An acute illness characterized by fever caused by infection with the bacterium Salmonella typhi. Typhoid fever has an insidious onset, with fever, headache, constipation, malaise, chills, and muscle pain. Diarrhea is uncommon, and vomiting is not usually severe. Confusion, delirium, intestinal perforation, and death may occur in severe cases. The disease is transmitted through contaminated drinking water or food. Large epidemics are most often related to fecal contamination of water supplies or foods sold on the streets. A chronic carrier state'excretion of the organism for more than a year'occurs in approximately 5 percent of cases. Vaccination is recommended for people traveling to high-risk areas, such as the Indian subcontinent and developing countries in Asia, Africa, and Central and South America where there is prolonged exposure to potentially contaminated food and drink. Typhoid vaccination is not 100 percent effective and is not a substitute for careful selection of food and drink.