The maturation goes up, and it can allow transmission of malaria. Another ingredient for these malaria outbreaks is the dramatic increase in the number of people moving quickly around the globe bringing the malaria infection back to the United States. Then all it takes is a mosquito. The mosquito must bite someone with malaria and then bite someone else who didn't have it, and then transmit it to them. Still, all these ingredients do not yet add up to a major malaria outbreak.
Mosquito control remains the best defense.
What scientists worry about, even more, are viruses which can also thrive in extreme weather conditions, and outbreaks that can come as a complete surprise. As diseases move to new geographic areas, they interact with pre-existing diseases that are already there, and they swap genes, they evolve, and new agents can come out of that. Public health officials were caught off guard this summer in New York, by a virus never spotted before in the United States. We had not tested for West Nile, so it wasn't even on our radar screen. The West Nile-like fever outbreak escaped detection by routine public health measures.