Cholera

Cholera is an acute bacterial intestinal infection caused by toxigenic Vibrio cholerae O-group 1 or O-group 139. Many other serogroups of V. cholerae , with or without the cholera toxin gene (including the nontoxigenic strains of the O1 and O139 serogroups), can cause a choleralike illness. Only toxigenic strains of serogroups O1 and O139 have caused widespread epidemics and are reportable to the World Health Organization (WHO) as “cholera.” V. cholerae O1 is the source of an ongoing global pandemic, while the O139 serogroup remains localized to a few areas in Asia.

V. cholerae O1 has 2 biotypes, classical and El Tor, and each biotype has 2 distinct serotypes, Inaba and Ogawa. The symptoms of infection are indistinguishable, although more people infected with the El Tor biotype remain asymptomatic or have only a mild illness. Globally, most cases of cholera are caused by O1 El Tor organisms. In recent years, an El Tor variant that has characteristics of both classical and El Tor biotypes and may be more virulent than older El Tor strains has emerged in Asia and spread to Africa and the Caribbean. This strain is responsible for the epidemic on Hispaniola and appears to cause a higher proportion of severe episodes of cholera with the potential for higher death rates.