Cholera in its present day scenario.

Cholera existed in many parts of the world since olden days. Gangetic delta is considered as the home of the disease. Since 1970 there has been a significant development of the disease with its ecologic and epidemiologic aspects. Vibrio cholerae non-01 strain in taxonomically separated from V cholerae 01 strain. Though 01 strain causes epidemic outbreaks, still non-01 has been implicated to cause cholera like illness. While humans are long considered to be the only reservoir of V cholerae 01 strain, but the organism appears to have a free-living cycle in the natural environment. The organism survives more rapidly in the brackish water than fresh water. It has been demonstrated that V cholerae undergoes conversion to a viable but non-culturable state, whereby the cells are reduced in size, become ovoid, but in contrast to starved cells, do not grow at all on standard laboratory media. Seasonality coupled with starvation response and dormancy phenomenon, reflects the origin of V cholerae as an autochthonous estuary dweller. All biotypes of this organism can grow on media containing chitin as the sole carbon source. Outbreaks of the disease are related to plankton blooms associated with warmer sea-surface temperature. In 1997 V cholerae 01 biotype El tor continued to occur in all regions of the world. In 1982 a new classical variant initially displaced entrenched El tor in Bangladesh and coexisted with it for almost a decade. V cholerae 0139 Bangal has arisen along the Bay of Bengal and has spread in Asia.