I generally tend to steer clear of theological or philosophical musing on science threads, but as long as you brought it up to me....
Extending your implication that the flood did occur, and there was an ark, what makes you discount that the ancestors to today's diseases couldn't have been waterborne, or at least hitched rides on aquatic hosts?
Waterborne gonorrhea? Find me some of that and a lot of disreptuable men now have a credible excuse to give their wives.