State asks doctors to watch for mosquito-borne virus

State health officials are asking doctors to begin watching for signs of a mosquito-borne disease that has grown increasingly common in Latin America.

Zika virus has spread across more than a dozen countries since transmission was first documented in the Western Hemisphere last May. It typically causes mild illness that can include fever, rash and joint pain. But infections in some pregnant women have been linked with a rare condition that causes brain damage and abnormally small heads in newborns.

Last week, federal health officials urged pregnant women to consider postponing travel to any area where Zika virus is circulating.

The mosquito that transmits most cases of Zika virus does not live in Minnesota. But the tropical and subtropical weather conditions that the Aedes aegypti mosquito favors also lure thousands of winter-weary Minnesotans — raising their risk of contracting the disease.

The Minnesota Department of Health says doctors should consider the Zika virus when evaluating sick travelers who have returned recently from parts of Central and South America, Mexico and the Caribbean.

Epidemiologist Dave Neitzel said Minnesota has had only one documented case of travel-related Zika infection so far.

"That was actually back in 2014, a Minnesota resident that traveled out of country to somewhere in Asia," he said. "But we are going to be watching for cases that occur here in the Americas too."

Although travel to Zika hot spots still poses the most significant risk to Minnesotans, it's possible that the virus could spread locally under the right circumstances. A mosquito species called the Asian tiger can also transmit Zika virus, Neitzel said, and Asian tiger infestations have been detected in Minnesota more than a dozen times since 1991.

The mosquitoes don't come here on their own, Neitzel said. They get a ride.

"Usually in shipments of tires that have come into Minnesota, oftentimes for recycling or reuse," he said. "If those tires sit outside for a long time they can produce mosquitoes."

Minnesota's harsh winters have so far prevented Asian tiger mosquitoes from gaining a foothold here. But that could change with global warming. There are populations as far north as Chicago.

Still, Neitzel said, their numbers are minuscule compared to other pest mosquitoes that are adapted to this climate. "I don't think we have the mosquitoes here right now to really maintain the virus locally," he said.

Researchers don't think that native mosquitoes in Minnesota are capable of transmitting Zika virus. But Neitzel said that since this is an emerging outbreak, there are still a lot of questions about what's possible.

Since there is no treatment or vaccine yet, Neitzel said, the best protection for people traveling to Zika-endemic areas is mosquito repellent, protective clothing and housing that has secure screens on windows and doors.