Prospective study of the incidence of diarrhoea and prevalence of bacterial pathogens in a cohort of Vietnamese children along the Red River

We prospectively studied diarrhoea incidence among 1655 children < 5 years of age in northern Vietnam for 1 year using primarily passive surveillance. Standard culture methods were used to detect bacterial pathogens. Overall 2160 cases occurred (1.3 cases/child per year). Peak rates of diarrhoea occ urred in children < 12 months old. Rates ranged from 3.3 cases/child per ye ar in children < 1 year old, to 0.7 cases/child per year in 4-year-olds. Ca mpylobacter, shigella and enterotoxigenic Escherichia coli were most common ly isolated. Rates detected by active surveillance were about twice those d etected passively. S. flexneri was the most common shigella serogroup (65%) . S. flexneri serotypes 6, 4, 1 and Y were most common, but 40% were untypa ble using commercial antisera. The data illustrate important regional diffe rences in pathogen prevalence and shigella serotype distribution. Shigella vaccine development strategies, commonly targeting S. flexneri 2a, S. sonne i and S. dysenteriae 1, will have little impact on diarrhoea rates in Vietn am.