The mosquito species driving the ongoing Zika virus outbreak appears to range over a far wider swath of the continental United States than previously estimated, stretching as far north as Ohio in the Midwest and New Jersey along the East Coast.

The revised estimates, based on a newly released map from the Centers for Disease Control and Prevention, suggest a far larger US population than previously believed could be exposed to the virus when mosquito season ramps up.

Experts call Aedes aegypti, or the yellow fever mosquito, an optimal insect to transmit Zika because they get infected themselves relatively easily, like to live among people, and prefer to feed on people instead of other animals.

They become infected by taking a blood meal from an infected person, and they pass the virus on as they bite other people after becoming infectious.

The CDC’s previous map indicated Aedes aegypti stuck along the hot and humid Gulf Coast; reached into Georgia and South Carolina; and appeared in pockets in the Southwest and California. The new map shows they might be distributed throughout the South and Southwest, and stretch into states including Maryland, West Virginia, and Kentucky.

Some studies have also shown that another species of Aedes mosquito — the albopictus, or Asian tiger mosquito — can likely spread the virus as well. But albopictus mosquitoes have a broader diet and don’t spend as much time around people as aegypti mosquitoes.

The CDC’s new maps, which present only the approximate distribution of the mosquitoes, show albopictus mosquitoes also live in a wider area than the prior map indicated. They can appear in most of the southern half of the country, reach through the Midwest into Minnesota, and span all the way into New York and New England.

So far, no mosquito-transmitted cases of Zika have appeared in the continental United States, but some experts say as temperatures rise and mosquitoes become more active, that will likely change.

The concern with Zika is not so much the sickness the virus itself causes: Most people who contract the virus don’t show symptoms, and those that do have to deal with a few days of rash, fever, and head and body aches.

But health officials are concerned that the virus causes other complications. Pregnant women who contract the virus appear to face higher risks of their children being born with birth defects, including a condition called microcephaly, in which the brain does not develop fully.