INTRODUCTION
Enteric fever is characterized by severe systemic illness with fever and abdominal pain [1]. The organism classically responsible for the enteric fever syndrome is Salmonella enterica serotype Typhi (formerly S. typhi). Other Salmonella serotypes, particularly S. enterica serotypes Paratyphi A, B, or C, can cause a similar syndrome; however, it is usually not clinically useful or possible to reliably predict the causative organism based on clinical findings [2]. Humans are the only reservoir for S. Typhi and S. Paratyphi A. The term "enteric fever" is a collective term that refers to both typhoid and paratyphoid fever, and "typhoid" and "enteric fever" are often used interchangeably.The epidemiology, microbiology, clinical manifestations, and diagnosis of enteric fever will be reviewed here. The pathogenesis, treatment and prevention of enteric fever are discussed separately. (See "Pathogenesis of enteric (typhoid and paratyphoid) fever" and "Enteric (typhoid and paratyphoid) fever: Treatment and prevention" and "Immunizations for travel".)
EPIDEMIOLOGY
Worldwide — Worldwide, enteric fever is most prevalent in impoverished areas that are overcrowded with poor access to sanitation.
Incidence estimates suggest that south-central Asia, Southeast Asia, and southern Africa are regions with high incidence of S. Typhi infection (more than 100 cases per 100,000 person-years) [3-6]. As an example, in a prospective study performed in India between 2017 and 2020, weekly surveillance for acute febrile illness was performed among more than 24,000 children ages 6 months to 14 years in three urban sites and one rural site [7]. The risk of typhoid fever (confirmed by blood culture) was greater in urban areas; at the three urban sites, the incidence ranged from 576 to 1173 cases per 100,000 child-years; at the rural site, the incidence was 35 cases per 100,000 child-years. The risk was greater in larger households with fewer assets and without a sanitary toilet.
Other regions of Asia and Africa, some parts of Latin America, the Caribbean, and Oceania have a medium incidence of 10 to 100 cases per 100,000 person-years. These estimates, though, are limited by lack of consistent reporting from all areas of the world and are based on extrapolation of data across regions and age groups. Contemporary population-based studies from Latin America, in particular, are lacking, and surveillance suggests that rates have declined substantially over the past 30 years, though intermittent outbreaks continue to occur [8]. Furthermore, subsequent data from Africa have revealed substantial heterogeneity between countries, with some Southern and Northern African countries having very low rates (<5 cases per 100,000 person-years) while several countries in Eastern and West Africa have rates >100 per 100,000 [9]. S. Paratyphi A remains uncommon in Africa [9], but accounts for a substantial proportion of enteric fever cases in areas of South Asia [10].