Perhaps, you can avoid the unnaturally tepid waters that nurture dreadful bacterium. Tropical mosquitoes — already the deadliest scourge in human history — will be tougher to elude. Warmer temperatures will extend the range of vectors that transmit malaria, Zika, West Nile, dengue, Chikungunya, various encephalitides and yellow fever. Mosquitoes, doing most of their killing in the tropics, already cause 700,000 to a million deaths a year.