When a country as perpetually stricken with both natural and man-made disasters as Haiti, which is also the poorest country in the Western Hemisphere and has a history of political instability, it ordinarily would not be surprising to have a disease normally associated with natural disasters start to spread among the population. In the case of the cholera outbreak in Haiti, which started following the 2010 earthquake, the possible cause and impact have caught many people off guard, and many Haitians demanding answers.
Cholera is generally caused by contaminated drinking water usually associated with poor sanitary practices or, more often, a sanitation system massively disrupted by floods, earthquakes, or war. In the case of Haiti, which has a long history of substandard sanitation practices, the scene could have been set for a cholera outbreak following the earthquake. It appears, however, that this outbreak may have been inadvertently introduced into Haiti by United Nations peacekeeping forces dispatched to the country to help maintain order after the disaster and to aid in providing shelter, food and medicine. It has been alleged that peacekeeping troops from Nepal, who operated out of a base situated on the banks of a river, were responsible for the outbreak. If human waste from the military base was going into the water supply, then a common result would be cholera.
The questioner inquired about the impact on the environment of the cholera outbreak. In general, the cause-effect relationship is reversed. As pointed out, cholera is usually a result of substandard environmental conditions, not the other way around.
Anytime a natural disaster strikes a part of the developing world, or even the developed world, public health officials worry about cholera outbreaks. That the outbreak in Haiti has stretched into its third year, and left around 8,000 dead with hundreds of thousands more infected, is indicative of the difficulty of stemming such a disease in a desperately poor region where conditions were never good to begin with.