Mosquito-Borne Encephalitis​ Virus Strikes In LA

LOS ANGELES, CA — The first human case of Saint Louis encephalitis to hit Los Angeles County in decades has struck in the San Fernando Valley where an elderly resident contracted the mosquito-borne illness.

The Los Angeles County Department of Public Health Monday announced the disease, which the region hasn't seen since 1997. To date, only one batch of mosquito samples has tested positive for the virus in the Playa Vista area. The valley resident was sickened with the virus in late August, according to the health department.

The virus can be fatal, and there is no vaccine against it. Health officials are calling on residents to protect themselves by avoiding mosquito bites.

"Since Saint Louis encephalitis is transmitted to people through the bite of an infected mosquito, the best way to prevent getting infected is to prevent mosquito bites," said Dr. Muntu Davis, Los Angeles County's health officer. "Residents should protect themselves by using EPA-registered repellent to keep mosquitoes from biting you, and checking for items that collect standing water in their homes or yards where mosquitoes can breed to tip out the water."

The virus is similar to the West Nile virus in that it can be deadly in some people while showing no symptoms in others. Saint Louis encephalitis affects the nervous system and can lead to infection on the brain, paralysis and death in severe cases. However, most people who carry the virus don't even know they have it. The majority infected have no or mild symptoms, health officials said. There is no preventive vaccine, and only supportive treatment is available.

People over 50 years old or individuals with lowered immune systems are at greater risk of experiencing severe symptoms if infected, which include fever, headache, stiff neck, confusion and decreased alertness. Anyone with symptoms should contact their health care provider.

To decrease the risk of infection:

-- Use mosquito repellents to keep mosquitoes from biting you. EPA- registered repellents containing DEET, picaridin, IR3535 and oil of lemon eucalyptus are the longest lasting and most effective. Take precautions particularly at dawn and dusk when mosquitoes that spread West Nile and Saint Louis encephalitis are most active.

-- Make sure that doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes.

-- Mosquitoes lay eggs even in small amounts of standing water, including standing water in flowerpot saucers, old car tires, rain gutters, rain barrels and pet bowls. Check such items each week and cover, clean or clear them out.

-- Clean and maintain swimming pools, spas. Drain water from pool covers.

-- Stock garden ponds or artificial lakes with mosquitofish or other mosquito-eating fish. Contact your local Vector Control District to place service requests, report mosquito problems, request mosquitofish, and report neglected pools or standing water where mosquitoes breed.

More information and resources can be found at:

-- Los Angeles County Department of Public Health: http://publichealth.lacounty.g...

-- California Department of Public Health: https://www.cdph.ca.gov/Progra...

-- Centers for Disease Control and Prevention: https://www.cdc.gov/sle/

-- log onto http://www.socalmosquito.org for information about mosquito control and how to find your local vector control district.

For questions about mosquitoes, residents can call:

-- Greater Los Angeles County Vector Control District: (562) 944-9656;

-- Los Angeles County West Vector Control District: (310) 915-7370;

-- San Gabriel Valley Mosquito and Vector Control District: (626) 814-9466;

-- Antelope Valley Mosquito and Vector Control District: (661) 942-2917;

-- Compton Creek Mosquito Abatement District: (310) 933- 5321;

-- Pasadena City Health Department: (626) 744-6004; or

-- City of Long Beach Vector Control Program: (562) 570-4132.

City News Service and patch staffer Paige Austin contributed to this report. Photo: Shutterstock