As rapid global travel increases and global warming allows tropical vectors to move into areas previously unoccupied we are going to start to see tropical diseases become regular visitors to the mainland US.

We saw this with West Nile virus.

Now this:
http://www.wired.com/wiredscience/2010/09/disease-mosquitoes-climate-change-uh-oh/

Here in WA, we can't get temps warm enough for three consecutive days to even develop a decent crop of heartworm-carrying mosquitoes.

Sue