I don't know if we have ever had Malaria here but yellow fever was a killer in Galveston and New Orleans in the past. I don't know what would have to happen to bring it back.
"I don't know if we have ever had Malaria here"
Actually, yes there was malaria in the southern U.S. Just to point out an "environmentalist" link, I believe John Muir contracted it, don't recall where exactly (Florida ?). If anything, that is a perfect example of how malaria can be eliminated from an area without the use of DDT. We have not used DDT here for years, but we have a very aggressive abatement program.