The first mosquito-related death in the San Francisco Bay Area and the detection of mosquitoes carrying West Nile virus in Southern California underscore the risk Californians face as they spend more time outdoors this summer.
But experts say there are simple preventative measures people can take to reduce their risk of being bitten and infected with the virus.
On July 16, a man who lived in eastern Contra Costa County died of West Nile virus infection, according to the county’s public health department. It was the first West Nile virus-related death reported in the county since 2006.
Contra Costa Health’s Communicable Disease Control Program is investigating the case and has not determined where the person was infected, according to a news release. The agency is not releasing further details about the case in order to “preserve medical confidentiality.”
Traces of West Nile virus were recently detected in the same area. The Contra Costa Mosquito and Vector Control District found one dead bird and five chickens that tested positive for the virus, all in the city of Oakley.
West Nile virus is transmitted to birds through the bite of an infected mosquito. A mosquito that feeds on an infected bird can then become infected with the virus. An infected mosquito can transmit the virus to a human or other animal.
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The infection can be dangerous for humans, with symptoms including fever, headache, vomiting and rash.
Two human cases of West Nile virus disease have been reported in Fresno and Yuba counties, according to the California Department of Public Health’s weekly arbovirus surveillance bulletin. In addition, three blood donors have tested positive for West Nile virus in Fresno County, although they were asymptomatic.
On July 26 alone, a total of 140 new West Nile virus-positive mosquito clusters were reported in 21 counties, including Los Angeles, Orange, Placer, Riverside, San Bernardino, Santa Clara, and Yuba. So far in 2024, 583 West Nile virus-positive mosquito clusters have been discovered in 24 counties.
Last month, Los Angeles County reported that mosquitoes carrying the virus had been collected in a trap in the Winnetka neighborhood of the San Fernando Valley.
In a statement, the Greater Los Angeles County Vector Control District said the presence of West Nile virus in the community is not unusual, but that “this early detection serves as a critical reminder to all residents to take preventative measures.”
What attracts mosquitoes?
According to the American Mosquito Control Assn., there are 30 types of mosquitoes in the United States. While there are differences between them (for example, some feed during the day and others at night), they share a life cycle that depends on the water in which they breed.
Six types of mosquitoes are found in California, but only the Culex mosquito can carry West Nile virus.
Vector control agencies attempt to eliminate public breeding sites in gutters, underground storm drains, flood control channels and debris basins. However, mosquito control is a shared responsibility and residents must do their part by eliminating potential breeding sites around their homes.
Start by identifying items on your property that can hold standing water, which, if left untouched for at least seven days, is a mosquito magnet. Typical sites include birdbaths, old tires, clogged gutters, portable basketball hoops, uncovered outdoor grills, potted plants with saucers and flower vases.
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Stagnant water that also contains leaves, dirt or grass clippings is a breeding ground for mosquitoes, according to the American Mosquito Control Assn.
Eliminate these breeding sites by draining or emptying the water and then preventing the buildup of other insects. For example, turn over a bucket of rainwater or cover your grill. Do this at least once a week.
How to scare away mosquitoes
The Los Angeles County Vector Control District suggests that residents apply an EPA-registered insect repellent containing one of these active ingredients: DEET, picaridin, IR3535 (a trade name for ethyl butylacetylaminopropionate), para-menthane diol, 2-undecanone (a plant-derived ingredient), or oil of lemon eucalyptus.
The Centers for Disease Control and Prevention advises against spraying insect repellent under your clothing. The agency also suggests that if you use sunscreen, apply the sunscreen first and then the insect repellent.
Alternatives to chemical sprays or creams include repellents made from plant ingredients such as citronella, lavender and peppermint. The American Mosquito Control Assn. said these ingredients are less effective than their synthetic counterparts, but they may work for people who don’t attract too many mosquitoes.
You can also try to make your outdoor recreation area mosquito-proof by installing several tiki torches or other devices that emit repellent. But the effectiveness of diffusers can vary depending on the species of mosquito.
For example, the Greater Los Angeles County Vector Control District says citronella candles are effective at repelling mosquitoes only in the immediate radius around the candle, and only in the absence of wind. It adds that Aedes mosquitoes prefer ankles, so candles that are typically placed on tables don’t offer much protection.
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Certain plants can also provide some level of protection for your patio. These include citronella and some other varieties of geranium, marigolds, lemongrass, catnip, some types of mint, lavender, and lantana. Some common herbs have limited ability to repel mosquitoes, such as rosemary, garlic, basil, thyme, and fennel.
Try them one by one until you find the approach that works best for you.
If despite all these precautions mosquitoes manage to bite you, do not scratch. Scratching can cause a secondary infection and prolong the irritation. In extreme cases, scratching bites can leave scars.
An anti-itch cream is usually all you’ll need to relieve the discomfort. If you’re severely allergic to mosquitoes, the American Mosquito Control Assn. says you may need a cream that contains Benadryl or a similar antihistamine.
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This article was originally published in the Los Angeles Times.