Why is New Orleans such a breeding ground for infectious disease?
In the 19th Century, New Orleans was well-known as a place for cholera. The region is considered the most tropical environment in the United States, and it has gone through cholera outbreaks; it has had typhoid fever; it has had salmonella and Campylobacter outbreaks. It has had epidemics in the past, but these epidemics have not occurred recently because of a better public health system.
What are some of the long-term health concerns in the regions affected by the floods?
The most immediate concerns are things that you can catch through contaminated water: typhoid fever, salmonella, cholera, etc. Since the entire city of New Orleans is underwater, there's clearly raw sewage there, too.
Hepatitis A is a food borne disease that you can get either through contaminated food or water, so it is also something these people have to worry about. Hepatitis A isn't a concern for those who have had the vaccine, but it is not a mandated vaccine in childhood. People are usually only vaccinated when they travel to countries where the risk is high, so I don't think the majority of Americans have received it.
What could be some of the potential contaminants of the water?
Animals and human feces are potential sources of bacteria, as well as pollutants and rotting, biological material.
At this point, what are some preventative steps people can take?
Well, if they don't have access to clean water, they need to boil their water for about twenty minutes. If they can't boil their water, there are tablets [available in many emergency kits] that precipitate out the organisms. If they can't get that, then they're at risk to catch these diseases.