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It's mosquito season: Who should wear insect repellent, and when



Morag Riddell via Flickr Creative Commons

Mosquitoes like it hot. As temperatures increase, so does the potential for the insects to bite - and possibly transmit diseases. That's a nationwide concern this summer, as the Zika virus rages through much of the Americas.

But health officials in Los Angeles and Orange counties are not currently recommending that everyone slather themselves in mosquito repellent all day long. At this point, they are mainly pushing people to protect themselves when they go outside at dawn and dusk.

The rationale is that for Southern California residents, the more pressing mosquito-borne disease is not Zika, but West Nile virus.

Here's why: While the Aedes aegypti mosquitoes, which carry Zika and several other infectious diseases, are in Southern California, none of the Aedes mosquitoes found so far in the state or nationwide were carrying Zika.

Meanwhile, most Southern California counties have reported mosquitoes testing positive for West Nile this year. Last year in the Golden State, there were 783 human cases of West Nile, 53 of which were fatal.

Aedes aegypti mosquitoes bite primarily during the daytime; Culex mosquito species, a number of which can carry West Nile, tend to bite at dawn and dusk.

"I would like to see the message first get out to do dawn and dusk," says Laurene Mascola, chief of the Acute Communicable Disease Control Program at the L.A. County Department of Public Health.

While anyone can develop severe illness from West Nile, like meningitis or encephalitis, Mascola says it's especially important for people over age 60 to follow this recommendation, since they are at greatest risk. People with certain medical conditions, including cancer and diabetes, and those who have received organ transplants are also at elevated risk, she says.

The repellent recommendation could be broadened if there are signs of Zika transmission within the country, says Mascola.

"If we feel that Zika is coming closer to being something that's a reality here in the U.S., which we are preparing for constantly, then of course we can be more vigilant, and then especially in that group, I would target, of course, pregnant women," she says.

The Centers for Disease Control and Prevention, meanwhile, is recommending that all pregnant women wear mosquito repellent daily to protect themselves and their babies against Zika. Contracting Zika virus during pregnancy can cause microcephaly and other severe brain defects, according to the CDC.

Tips on using mosquito repellent