Transmission
The bacteria which causes typhoid fever may be spread through poor hygiene habits and public sanitation conditions, and sometimes also by flying insects feeding on feces. Public education campaigns encouraging people to wash their hands after defecating and before handling food are an important component in controlling spread of the disease. According to statistics from the United States Centers for Disease Control and Prevention (CDC), the chlorination of drinking water has led to dramatic decreases in the transmission of typhoid fever in the U.S.A.
A person may become an asymptomatic carrier of typhoid fever, suffering no symptoms, but capable of infecting others. According to the CDC approximately 5% of people who contract typhoid continue to carry the disease after they recover. The most famous asymptomatic carrier was Mary Mallon (commonly known as "Typhoid Mary"), a young cook who was responsible for infecting at least 53 people with typhoid, three of whom died from the disease. Mallon was the first apparently perfectly healthy person known to be responsible for a Typhoid "epidemic".
In the early 20th century, many carriers of typhoid were locked into an isolation ward never to be released to prevent further typhoid cases. These people often deteriorated mentally, driven mad by the conditions they lived in.
Read more about this topic: Typhoid Fever