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In 2000, typhoid fever caused an estimated 21.7 million illnesses and 217,000 deaths. It occurs most often in children and young adults between 5 and 19 years old. In 2013, it resulted in about 161,000 deaths – down from 181,000 in 1990. Infants, children, and adolescents in south-central and Southeast Asia experience the greatest burden of illness. Outbreaks of typhoid fever are also frequently reported from sub-Saharan Africa and countries in Southeast Asia. In the United States, about 400 cases occur each year, and 75% of these are acquired while traveling internationally.
Historically, before the antibiotic era, the case fatality rate of typhoid fever was 10–20%. Today, with prompt treatment, it is less than 1%. However, about 3–5% of individuals who are infected develop a chronic infection in the gall bladder. Since S. e. subsp. enterica is human-restricted, these chronic carriers become the crucial reservoir, which can persist for decades for further spread of the disease, further complicating the identification and treatment of the disease. Lately, the study of S. e. subsp. enterica associated with a large outbreak and a carrier at the genome level provides new insights into the pathogenesis of the pathogen.
In industrialized nations, water sanitation and food handling improvements have reduced the number of cases. Developing nations, such as those found in parts of Asia and Africa, have the highest rates of typhoid fever. These areas have a lack of access to clean water, proper sanitation systems, and proper health-care facilities. For these areas, such access to basic public-health needs is not in the near future.