Cholera is an acute epidemic infectious disease caused by the bacterium Vibrio cholerae. A soluble toxin elaborated in the intestinal tract by the bacterium activates the adenylate cylase of the mucosa, causing active secretion of an isotonic fluid resulting in profuse watery diarrhea, extreme loss of fluid and electrolytes, and dehydration and collapse, but no gross morphologic change in the intestinal mucosa.
Vibrio cholerae bacteria naturally live as rod-shaped bacteria existing primarily in plankton populations in shallow, brackish water. Attaching themselves to microscopic crustaceans called copepods that exist as part of the planktonic ecosystem, they move naturally through several environments. Colonies of the bacteria can exist on the surface of the copepods, flourishing during times when temperature, low salinity and high nutrient levels cause algal blooms in the estuary, explaining why cholera has traditionally been associated with monsoon conditions.
The bacteria also, however, exist as colonies of biofilms coating the surface of various natural features of the estuary, covering the water surface but also plants, stones, shells and similar items. They can take non-active form and survive in the silt of the estuary.