A positive West Nile virus mosquito sample was collected in El Monte

West Covina, Calif. (July 29, 2025) — The San Gabriel Valley Mosquito & Vector Control District (SGV Mosquito/District) has confirmed West Nile virus (WNV) activity in its service area for the first time this season. The virus was detected in a mosquito sample collected from a surveillance trap in the city of El Monte.

“West Nile virus is a recurring concern in our region,” said Director of Scientific Programs Tristan Hallum. “It’s endemic to the San Gabriel Valley, meaning we expect to detect it every year in mosquitoes, birds, and occasionally humans. The key to staying protected is avoiding mosquito bites.”

West Nile virus is most often detected during the warmer months, when higher overnight temperatures accelerate mosquito breeding and viral transmission. SGV Mosquito will continue monitoring disease activity and controlling mosquitoes in public spaces through routine inspections and necessary treatments, but residents should take precautions to protect their health.

Mosquito control is a shared responsibility. The District urges residents to take an active role in reducing the threat of WNV in their communities by taking the following actions to stay healthy and bite-free:

• Tip out stagnant water around the home weekly;
• Toss unused containers that can hold stagnant water; and
• 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.

“There is no vaccine or cure for West Nile virus in humans,” said Hallum. “The best method of protection is prevention.”

For more information, residents can contact the San Gabriel Valley Mosquito and Vector Control District at 626-814-9466, online at SGVmosquito.org, or on social media: Facebook, X, and Instagram.

###

About SGV Mosquito
SGV Mosquito 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.

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.

MEDIA CONTACT

Anais Medina Diaz, Director of Communications

amedinadiaz@SGVmosquito.org | 626-814-9466