Most of the Northern United States and Canada, it is simply too cold for the mosquitoes that spread the Zika virus to survive. Aedes aegypti, the only mosquito confirmed to spread Zika, has been in the Southern United States since the 1960s, and pretty much all over South America since at least the 1990s. The other mosquito involved, Aedes albopictus, has never been shown to carry Zika, but scientists suspect that it probably could. As of 2010, however, there has been no sign of either mosquito species migrating northward.
The mosquitos could migrate north eventually. In fact, Aedes albopictus have been known to migrate along highways, laying their eggs in standing water loaded onto trucks. But even then, there is little risk of these mosquitos surviving long-term north of the Mason Dixon line. And, while a large portion of the U.S. gets warm enough during the summer for these mosquitos to survive, only Florida, Hawaii and the southern tip of Texas have climates that could sustain these mosquitos year-round.
The Lancet indicates there is seasonal outbreak risks in the southern US states. A seasonal outbreak would still mean millions of women in the US would have risks of deformed babies if they were or became pregant during the outbreak and for months after.
SOURCES – Lancet, Vocativ, USA Today,