West Nile mosquito
Mosquitoes can transmit the viruses that cause West Nile fever. Photo by Noah Poritz, courtesy United States Department of Agriculture Agricultural Research Service

Two mosquito samples taken in San Marino have tested positive for West Nile virus, bringing to three the number of positive mosquito samples in Los Angeles County this season, the Greater Los Angeles County Vector Control District announced Tuesday.

“The district will continue monitoring disease activity and controlling mosquitoes. WNV occurs every summer and may also be present in areas where it has not yet been detected,” Steve Vetrone, the agency’s director of scientific-technical services, said in a statement.

“As residents enjoy the outdoors throughout the summer, it is important they take precautions against mosquito-transmitted diseases like WNV by wearing insect repellent.”

According to the district, the positive San Marino samples were detected July 1. The previous positive sample was detected June 2 in Bellflower.

West Nile virus is endemic to the county, and warm temperatures can increase virus activity and mosquito populations, according to the agency.

Last year, 148 human West Nile cases were reported in California, including 17 in L.A. County. No human cases have been reported in the state so far this year, according to the California Department of Public Health.

Statewide, 138 mosquito samples have tested positive, and 14 dead birds have been found with the virus, the state health department reported.

A mosquito contracts the West Nile virus when it feeds on an infected bird. After that, the mosquito can transmit the virus to people through a bite.

Because there is no human vaccine or cure for West Nile virus, the agency recommends that residents be proactive by using mosquito repellents — but warns that no not all of them work equally well.

The Centers for Disease Control and Prevention recommend products with the active ingredients DEET, Picaridin, IR3535, or oil of lemon eucalyptus as being safe and effective against mosquitoes that can transmit diseases when used according to the labels.

The GLACVCD also recommends taking these additional steps:

— eliminate standing water in clogged rain gutters, rain barrels, discarded tires, buckets, watering troughs or anything that holds water for more than a week;

— ensure that swimming pools, spas and ponds are properly maintained;

— change the water in pet dishes, bird baths and other small containers weekly

— request mosquitofish from your local vector control district for placement in ornamental ponds, and

— report neglected (green) swimming pools in your neighborhood to your vector control district.

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