What causes typhoid fever?

Typhoid fever, also known as typhoid, is a disease caused by 'Salmonella' serotype 'Typhi' bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several days. This is commonly accompanied by weakness, abdominal pain, constipation, headaches, and mild vomiting. Typhoid fever is a type of enteric fever, along with paratyphoid fever. So far, 'S. enterica Typhi' is only known to infect and replicate within humans. Unlike other strains of 'Salmonella', no animal carriers of typhoid are known. Humans are the only known carriers of the bacterium

A typhoid vaccine can prevent about 40% to 90% of cases during the first two years. The vaccine may have some effect for up to seven years. For those at high risk or people traveling to areas where the disease is common, vaccination is recommended. Other efforts to prevent the disease include providing clean drinking water, good sanitation, and handwashing.

Children are most commonly affected. Typhoid decreased in the developed world in the 1940s as a result of improved sanitation and the use of antibiotics. According to statistics from the U.S. Centers for Disease Control and Prevention, the chlorination of drinking water has led to dramatic decreases in the transmission of typhoid fever.