Climate conditions hinder how far disease can spread. In the US, a warmer climate and the heavy, extended rains most likely helped spread the Hantavirus (Hantavirus is a type of virus carried by rodents and causes severe respirator infections in humans and, in most cases, hemorrhaging, kidney disease and ultimately death) In other places, a warmer world is helping expand the range of insects that carry disease like yellow fever. People who would normally not have to worry about such illnesses may soon have reason to worry.
Like cases of Hantavirus suddenly showing up in the United States, outbreaks of different disease have been reported in areas of South American and Africa that - until recently - had never seen before. For example, dengue fever in Mexico has spread above its former elevation limit of 3,300 feet and has appeared as high 5,600 feet. While in Columbia, the mosquitoes that carry dengue and yellow fever viruses were previously limited to 3,300 feet but have been recently found at 7,200 feet! (Epstein, P.)