Typhoid fever in Bangladesh: implications for vaccination policy.

OBJECTIVE: To describe the age-specific distribution of typhoid fever including the degree of Salmonella typhi bacteremia among patients evaluated at a large private diagnostic center in Bangladesh, a highly endemic area.
METHODS: We conducted a prospective-, passive- and laboratory-based study to identify patients with S. typhi bacteremia. Subjects (n = 4,650) from whom blood cultures were obtained during 16-month period were enrolled from private clinics and hospitals throughout Dhaka. Isolation and quantification of S. typhi from blood cultures were performed by the lysis direct plating/ centrifugation method.
RESULTS: Bacterial pathogens were recovered from blood of 538 of 4,650 patients (11.6%) evaluated. S. typhi was the single most common pathogen recovered, comprising nearly three-fourths of isolates (72.7%; 391 of 538). Isolation rate of S. typhi was highest in monsoon and summer seasons and lowest in winter months. The majority (54.5%; 213 of 391) of S. typhi isolates were from children who were younger than 5 years, and 27% (105 of 391) were from children in the first 2 years of life. The isolation rate was highest (17.4%, 68 of 486) in the second year of life. The number of bacteria in blood on the basis of colony-forming units per ml of blood by age group was inversely related to age.
CONCLUSIONS: Detection of S. typhi bacteremia in young children in Dhaka, Bangladesh, was considerably higher than previously appreciated, with a peak detection rate in children < or =2 years of age, indicating the need to reassess the age-specific burden of typhoid fever in the community on a regional basis. Contrary to current recommendations this study suggests that development of new vaccines should target infants and young children.