Editing Vibrio cholerae (section)

==Diversity and evolution==
Two [[serotype|serogroups]] of ''V. cholerae'', O1 and O139, cause outbreaks of cholera.  O1 causes the majority of outbreaks, while O139 – first identified in [[Bangladesh]] in 1992 – is confined to Southeast Asia. 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 cholera-like illness. Only toxigenic strains of serogroups O1 and O139 have caused widespread epidemics.

''V. cholerae'' O1 has two biotypes, classical and [[El Tor]], and each biotype has two 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. In recent years, infections with the classical biotype of ''V. cholerae'' O1 have become rare and are limited to parts of Bangladesh and [[India]].<ref>{{cite journal |last1=Siddique |first1=A.K. |last2=Baqui |first2=A.H. |last3=Eusof |first3=A. |last4=Haider |first4=K. |last5=Hossain |first5=M.A. |last6=Bashir |first6=I. |last7=Zaman |first7=K. |title=Survival of classic cholera in Bangladesh |journal=The Lancet |volume=337 |issue=8750 |pages=1125–1127 |year=1991 |doi=10.1016/0140-6736(91)92789-5|pmid=1674016 |s2cid=33198972 }}</ref> Recently, new variant strains have been detected in several parts of Asia and Africa. Observations suggest these strains cause more severe cholera with higher case fatality rates.