The official first day of summer is just a week away, and public health officials are preparing as best they can for local outbreaks of Zika. With 40 million people traveling back and forth between the U.S. and various Zika-affected countries every year, the Centers for Disease Control and Prevention says, local transmission is inevitable.

Late last week, the agency held a briefing with governors from the states most likely to be hit with localized Zika outbreaks (Alabama, Arizona, Florida, Louisiana, Mississippi, Texas, Georgia, Hawaii, and California). The states reviewed preparedness plans that include CDC Emergency Response Teams (CERT), ready to deploy to any state where an outbreak occurs.

"There's a lot of different parts to the Zika response," says Dr. Janet McAllister, head of the CDC vector team. "It involves entomologists, epidemiologists, and healthcare providers."

Part of that effort involves identifying where the mosquitoes capable of spreading Zika are most likely to live in the U.S. And new maps, created by the CDC and published in the Journal of Medical Entomology, can help in that effort. 

Here is more on the map, plus some other Zika updates from the past several days.

The Latest Zika Mosquito Map

New Maps Show Where Zika Mosquitoes Can Live in the U.S.
Aedes Aegypti mosquitoes are aggressive biters that have been responsible for most cases of Zika in South America and the Caribbean so far.

The new maps don't show where mosquitoes actually carrying Zika have been identified. So far, no such mosquitoes have been found in the U.S. Instead, they show the counties in the U.S. where the species of mosquitoes known to be capable of spreading the disease have been found at least once since 1995.   

The new maps include two kinds of Aedes mosquitoes: Aedes aegypti, an aggressive biter that's been linked to most Zika cases in South America and the Caribbean so far; and Aedes albopictus, a less aggressive species that is also thought to be capable of transmitting the disease.  

The Aedes aegypti mosquitoes have been found mostly along the Gulf Coast from Florida to Texas but also in New Mexico, Arizona, and Southern California as well as up the East Coast as far as Washington, D.C. Altogether, the species has been reported in 183 counties in 26 states.

The Aedes albopictus are more widespread, with reports in 1,241 counties in 40 states, and are especially common in the eastern half of the U.S.

The findings may be cause for alarm, but not for total panic: for a local outbreak to occur, mosquitoes have to do more than just survive in a certain region and climate; they have to actually thrive, reproducing enough to reach a certain population-density threshold.

The maps show where mosquitoes have been found, but they don’t indicate how likely that population threshold is to be reached in any given state, or where they have been found to carry the Zika virus.

Aedes Aldopictus mosquitoes are more common in the U.S. than the Aedes Aegypti species, but are less aggressive and less clearly linked to Zika.

What the WHO Meant to Say About Zika and Pregnancy

In a somewhat confusing announcement late last week, the World Health Organization said that men and women of reproductive age who lived in Zika-affected countries, should be “informed and orientated to consider delaying pregnancy.” Media outlets everywhere misinterpreted this statement to mean that the organization was advising couples to delay pregnancy. WHO officials have since clarified it: Couples in those countries who are considering becoming pregnant should not be nudged one way or the other. They should, however, be given all the relevant information and allowed to decide for themselves.

So far the available evidence puts the risk of mother-to-fetus transmission at somewhere between 1 percent and 13 percent.

Men Without Symptoms

French epidemiologists have reported a case of sexual transmission from an asymptomatic male—the first documented incident of its kind. So far all cases of sexual transmission have involved symptomatic men passing the virus on to their partners. It has been an open question whether or not asymptomatic men could also transmit the virus sexually. The answer for now is a tenuous yes, though researchers are working to understand why asymptomatic transmission is so rare, and what this one case can tell us about the virus overall.