Understanding_the_historical_spread_of_cholera_from_West_Africa_to_South_America_in_the_1990_S

Vibrio cholerae is the causative agent of cholera, an acute life-threatening diarrhoeal disease endemic in many developing countries and responsible for seven pandemics. There are more than 200 known serogroups of Vibrio cholerae, however only two, O1 and O139 cause cholera. V. cholerae O139 strains were identified as the causative agent for a cholera epidemic that broke out in parts of Bangladesh and India between 1992 and 1993. These serotypes are further differentiated into two biotypes (Classical and El Tor) based on genotypic and phenotypic differences. Since 1817 all of the early pandemics were exclusively attributable to strains of the classical biotype. However, by the 1960's El Tor replaced the classical biotype as the major cause of cholera. The re-emergence of classical strains in Bangladesh in 1982 resulted in a temporal overlap during which both biotypes co-existed for around a decade, however the classical biotype now seems to be extinct. New hybrid variants of V. cholerae O1 that display representative traits of both biotypes have recently been isolated. Thus, genotypic traits that have traditionally been viewed as distinguishing features of a particular biotype are now of limited value. Our current work is aimed at understanding the sequence diversity held within this species.