There's a worrisome problem at the heart of the Zika virus crisis that no one is talking about

With public health experts scrambling for answers to the Zika virus that's spreading rapidly throughout the Americas, a number of theories have come out trying to answer "why now?"

Some, like the one that claims it's all genetically modified mosquitoes' fault, are a bit wacky.

Others, like theory that it might have something to do with the rising prevalence of another mosquito-borne virus called dengue, seem a bit more probable.

A third theory certainly seems to hold water: A warming planet is allowing disease-carrying mosquitoes to thrive.

None of these, of course, are mutually exclusive. Both the rising prevalence of dengue and a gradually warming planet could both be affecting the current outbreak of Zika. And warmer temperatures - like the hottest year on record recorded last year, the same year Zika arrived in Brazil - are increasingly worrisome because they make it easier for the mosquitoes that transmit the virus to breed.

Aedes aegypti mosquitoes prefer damp, warm, indoor areas. And because they don't travel too far, dense urban areas are ideal living locations. As the World Health Organization said recently, it's "people, rather than mosquitoes" that move the virus from one community to another.

Still, the ranges in which mosquitoes can survive in thrive are expanding as the globe gets warmer, including to places further in the north in the US where the Aedes aegypti was not present before.

"As we get continued warming, it's going to become more difficult to control mosquitoes. The warmer it is, the faster they can develop from egg to adult, and the faster they can incubate viruses," Andrew Monaghan, a researcher at the National Center for Atmospheric Research, recently told The New York Times.

Luckily, the US has a lot going for it in terms of preventing mosquito bites. Air conditioning, window screens, and less densely populated urban areas, are all reasons the CDC does not expect it to be much of a threat to the majority of the continental US.

But as climate scientists have warned for years, a warmer planet will affect the spread of disease - especially those carried by insects and other pests which thrive at certain temperatures - and we may be seeing the signs of this now.