Cholera is caused by infection with cholera toxin-producing strains of Vibrio cholerae O1 or O139. Infected persons may suffer profuse dehydrating watery diarrhoea and death, a milder diarrhoeal illness, or no symptoms. In 2003, the World Health Organization reported 111 575 cholera cases and 1894 cholera deaths (WHO 2004). These numbers are believed to be an underestimate, because of underreporting and limited resources available for laboratory confirmation and routine surveillance. In areas with poor water and sanitation infrastructure, a small cluster of cholera cases can rapidly develop into a large epidemic (Anonymous 1995). Outbreaks often occur in refugee camps or remote rural areas, or during periods of civil conflict, when inadequate financial resources and geographic remoteness limit access to laboratory facilities, thereby delaying confirmation of cholera epidemics (Anonymous 1995; CDC 1997, 2003). In these settings, sensitive diagnostic tests that can be performed by field personnel with minimal laboratory infrastructure would allow for rapid confirmation of suspected cholera outbreaks and early resource mobilization for epidemic control.
Infection with toxigenic V. cholerae O1 strains is confirmed microbiologically by culture of stools or rectal swabs, and serogrouping and toxin testing of isolates. Traditional culture techniques often take ≥48 h to complete. Several diagnostic assays have been developed to detect V. cholerae O1 in stool more rapidly. We evaluated three of these assays in Dhaka, Bangladesh and examined whether test validity was related to the skill level of the technician.