Seroepidemiologic survey of epidemic cholera in Haiti to assess spectrum of illness and risk factors for severe disease.

To assess the spectrum of illness from toxigenic Vibrio cholerae 01 and risk factors for severe cholera in Haiti, we conducted a cross-sectional survey in a rural commune with more than 21,000 residents. During March 22-April 6, 2011, we interviewed 2,622 residents >= 2 years of age and tested serum specimens from 2,527 (96%) participants for vibriocidal and antibodies against cholera toxin; 18% of participants reported a cholera diagnosis, 39% had vibriocidal titers >= 320, and 64% had vibriocidal titers >= 80, suggesting widespread infection. Among seropositive participants (vibriocidal titers >= 320), 74.5% reported no diarrhea and 9.0% had severe cholera (reported receiving intravenous fluids and overnight hospitalization). This high burden of severe cholera is likely explained by the lack of pre-existing immunity in this population, although the virulence of the atypical El Tor strain causing the epidemic and other factors might also play a role.