Typhoid fever in Bangladesh: implications for vaccination policy

Objective. To describe the age-specific distribution of typhoid fever inclu ding 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 t o identify patients with S. typhi bacteremia. Subjects (n = 4650) from whom blood cultures were obtained during 16-month period were enrolled from pri vate clinics and hospitals throughout Dhaka. Isolation and quantification o f S. typhi from blood cultures were performed by the lysis direct plating/ centrifugation method. Results. Bacterial pathogens were recovered from blood of 538 of 4650 patie nts (11.6%) evaluated. S, typhi was the single most common pathogen recover ed, comprising nearly three-fourths of isolates (72.7%; 391 of 538). Isolat ion rate of S, typhi was highest in monsoon and summer seasons and lowest i n 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 fro m 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 mi of blood by age group was inve rsely related to age, Conclusions. Detection of S, typhi bacteremia in young children in Dhaka, B angladesh, was considerably higher than previously appreciated, with a peak detection rate in children less than or equal to2 years of age, indicating the need to reassess the age-specific burden of typhoid fever in the commu nity on a regional basis, Contrary to current recommendations this study su ggests that development of new vaccines should target infants and young chi ldren.