Typhoid is endemic to many countries. The risk of adult typhoid is greatest for international travellers going to countries with warm climates and underdeveloped sanitary facilities for sewage disposal and water treatment (especially developing countries in Latin America, Asia and Africa). School-aged children are at a higher risk of contracting the disease, although it is not as severe in children younger than 2 years old. The most recent statistics available indicate that there are fewer than 500 cases per year reported in the United States, and more than 60% of these occur in travellers to other countries.
This is one of the diseases being explored because of its value in biological warfare.