First Human Case of West Nile Virus Reported in Los Angeles County for 2021 | Public Health

All residents should take precautions against mosquitoes

The Los Angeles County Department of Public Health (Public Health) has identified the first case of human West Nile virus (WNV) infection in Los Angeles County for the 2021 season (excluding Long Beach and Pasadena as cases identified in those cities are reported by their local health departments). A resident of the South Bay area was hospitalized with WNV fever in late July and is recovering.

“We all have to take steps to prevent West Nile virus infections. Spread by mosquitoes, this virus is the leading cause of mosquito-borne disease in the continental United States. There are no vaccines to prevent or medications to treat WNV in people. Mosquitoes bite during the day and night. So, once a week empty and scrub, turn over, cover or throw out items that hold water, both indoors and outdoors. This stops mosquitoes from laying eggs in or near water. Protect yourself and family from mosquito bites by using EPA-registered mosquito repellent products, as directed, and wear clothing that covers arms and legs, especially during the peak mosquito season which lasts from June to November in Los Angeles County,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer.

West Nile virus is spread by the bite of an infected mosquito. Symptoms may include fever, headache, nausea, body aches, and a mild skin rash. WNV can affect the nervous system and result in meningitis, encephalitis, paralysis and even death. Adults over the age of 50 years old and people 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.

Public Health recommends the following actions to reduce the risk of West Nile virus infection:

  • Avoid mosquito-infested areas at dawn and dusk.
  • Use insect repellant. Use Environmental Protection Agency (EPA)-registered repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women. Find the right insect repellent for you by using EPA’s search tool.
  • Cover up. Consider wearing long-sleeved shirts and long pants when you are outdoors, particularly at these times and in areas where more mosquitoes are present.
  • Take steps to control mosquitoes indoors and outdoors.
  • Use screens on windows and doors. Check for and repair holes in screens to keep mosquitoes outdoors.
    • Stop mosquitoes from laying eggs in or near water. Once a week, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pet bowls, flowerpot saucers, rain barrels, or other containers. These are where mosquitoes lay eggs.
    • Empty and wash birdbaths and wading pools weekly.
    • Clean and chlorinate swimming pools; drain any water collecting on pool covers.
    • Stock garden ponds with mosquitofish (Gambusia affinis), goldfish, Koi or other mosquito-eating fish. These feed on mosquito eggs and larvae.

Public Health continues to document human cases of WNV every year in LA County, at an average of 118 cases per year during the previous 5 years. However, the total number of people infected with WNV each year in LA County is much higher as most infected persons do not experience any illness or only mild illness. These cases are neither reported nor recognized as WNV.

About three-quarters of reported cases have had severe disease and approximately 9% of patients with severe WNV die from complications. Public Health collaborates with local vector control agencies to target areas for mosquito control activities as well as educate people about how to protect themselves. There is no vaccine for WNV and no treatment to cure the illness once an individual becomes sick. Reduction of mosquito breeding sources and protection from mosquito bites are the best ways to prevent WNV infection.

“Keeping our neighborhoods safe from West Nile virus is a shared responsibility,” says Aaron Arugay, Executive Director of the Los Angeles County West Vector Control District. “Residents can reduce the risk of mosquito bites by eliminating standing water in their yards and using EPA-registered repellents when mosquito activity is observed.”

For more information on West Nile virus, visit http://publichealth.lacounty.gov/media/westnile. To find a local vector control district, visit http://www.socalmosquito.org.

Stagnant swimming pools or “green pools” should be reported to the Public Health Environmental Health Bureau at (626) 430-5200, or to a local vector control agency. Dead birds may be reported by calling (877) 968-2473 or online: https://westnile.ca.gov/report.php