Vibrio cholerae are curved rod-like bacteria of dimension 1.4-2.5 × 0.3-0.5 micrometers. Being very small, they flow freely suspended in water. They are not acid fast, though a high pathogen concentration when ingested, can conquer a weak digestive system. However, outbreak of an epidemic proportion overpowers even the persons possessing strongest immunity. Vibrio cholerae are transmitted only by the fecal-oral route, i.e., the organisms are excreted in the faeces, transmitted through water systems and must be ingested by people of newer regions, thereby spreading the disease rapidly.
It appears, however, that the Haiti outbreak may have been inadvertently introduced there by members of United Nations peacekeeping forces, who operated out of a base situated on the banks of Artibonite River river, a source of drinking water in Haiti. Compounding the initial outbreak, a massively devastating earthquake occurred 10 months later, leaving large numbers of people homeless, without proper sanitation or safe drinking water for an extended period of time. This made a bad situation worse by allowing the spread of the bacteria to flourish in Haiti.