The factors leading to the current Zika outbreak won’t be clear for some time, but environmental health experts say there’s a good chance such infectious diseases will become more common as the global climate warms. Mosquitoes, the blood-sucking insects responsible for transmitting Zika virus in Brazil and more than 20 other countries and territories in the Americas, are responsive to changing weather conditions, and experts warn they may increase in numbers as temperatures rise and as changes in precipitation levels create more standing pools of water — mosquitoes’ favorite breeding ground. More of the insects that host the virus could mean a higher chance of being infected.