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Mosquito control officials confirm first West Nile virus activity in Los Angeles County for 2021

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South Pasadena, Calif. (June 4, 2021) – The first indication of West Nile virus circulating in Los Angeles County in 2021 was detected in a dead crow collected in South Pasadena, the San Gabriel Valley Mosquito & Vector Control District (SGVMVCD) announced Monday, June 7, 2021.

Track West Nile virus activity for 2021

West Nile virus (WNV) is spread to people through mosquito bites. Birds can become sick from WNV, but do not spread the virus directly to people.

"West Nile virus is endemic, which means we'll detect it every year in our communities,'' said SGVMVCD Scientific Program Manager Melissa Doyle. "As the weather heats up, everyone should prevent mosquito bites and eliminate stagnant water around their home.''

Doyle urged everyone to take the following actions to stay healthy and bite-free:

  1. Tip out stagnant water around the home weekly;
  2. Toss unused containers that can hold stagnant water; and
  3. Protect against bites by using insect repellent containing any one of the following CDC-recommended ingredients: Picaridin, DEET, oil of lemon eucalyptus (or PMD), or IR3535.
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"It only takes one bite for a mosquito carrying West Nile virus to get you sick," warned SGVMVCD Public Information Officer Levy Sun. "Don’t take your chances and assume the next mosquito bite will be harmless.”

Mosquitoes in Southern California are generally more active from May to October.

"Mosquito control is a responsibility shared by all residents, businesses and property owners," Sun said.

For more information, or to report neglected swimming pools of stagnant water, visit or call 626-814-9466.

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About West Nile Virus
According to the Los Angeles County Department of Public Health, West Nile virus (WNV) is spread by the bite of an infected mosquito. One in five individuals infected with the WNV, for which there is no cure, will exhibit symptoms that include fever, headache, body aches, nausea or skin rash. The symptoms can last for several days to months. One in 150 people infected with the virus will require hospitalization. Severe symptoms include high fever, muscle weakness, neck stiffness, coma, paralysis and possibly death. Those at greatest risk include seniors and individuals with compromised immune systems. People over 50 years of age and those with chronic health problems are at higher risk of severe illness. While not all mosquitoes carry this virus, the type of mosquito that spreads this virus is found throughout Los Angeles County.

SGVMVCD is one of five vector control districts in Los Angeles County. Year-round, the agency monitors stagnant water sources, such as gutters, storm drains, channels and non-functional swimming pools. The agency also routinely monitors populations of adult mosquitoes using traps and tests groups of adult female mosquitoes for the presence of WNV and other mosquito-borne diseases. In addition, the agency submits samples from dead birds, such as crows, for testing, which can provide insight into the spread of WNV.