David88vert and mechman, here is a link to some literature that discusses v. cholera... The topic of the paper is climate change and the effect that has on infectivity of certain organisms, but if you skip down to page 759 and onwards, you'll see what I'm talking about. If the link will not let you access the paper, here is the citation:

Lipp, E.K., A. Huq, R.R. Colwell. 2002. Effects of global climate on infectious disease: the Cholera model. Clin. Microbiol.Rev. 4:757-770.

This is published info regarding mutations that result in a change in phenotype that result in the organism having a selective advantage. I'll come back n post on the rest later. Happy reading!