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 last week.
Scott Kwong, who serves as San Marino’s representative to the Greater Los Angeles County Vector Control District, said on Monday that mosquitoes infected with West Nile virus have previously been detected in this community. He said that San Marino had a mosquito that had tested positive for WNV as recently as August 2021. Kwong — who has been San Marino’s vector control representative since 2015 — was not aware of the last time San Marino had a human who contracted the disease.
WNV is the leading cause of mosquito-borne disease in the continental United States, according to the Centers for Disease Control and Prevention. It is most commonly spread to humans by the bite of an infected mosquito. Cases of the virus occur during mosquito season, which starts in the summer and continues through fall. There are no vaccines to prevent or medications to treat WNV in humans. Fortunately, most who are infected with WNV do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected humans develop serious, sometimes fatal, illness.
“The district will continue monitoring disease activity and controlling mosquitoes,” said Steve Vetrone, the agency’s director of scientific-technical services. “West Nile virus occurs every summer and may also be present in areas where it has not yet been detected. 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.
Last year, 148 human WNV cases were reported in California, including 17 in L.A. County. No human cases have been reported in the state 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 WNV 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 WNV, the agency recommends that residents be proactive by using mosquito repellents — but warns that not all of them work equally well.
The CDC recommends 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 Greater Los Angeles County Vector Control District 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.
- Report neglected (green) swimming pools in your neighborhood to your vector control district.
Kwong encouraged residents to contact him directly at scott.kwong@yahoo.com in the event neglected swimming pools are detected. He also said that mosquito repellents which are advertised as “natural” or “organic” have proven to be less effective.
Kwong is vice president of the Greater Los Angeles County Vector Control District and is slated to be president in 2023.
— City News Service contributed to this article.
