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Health officials in Los Angeles County are reporting the first human case of Saint Louis encephalitis (SLEV) in the county since 1997. The patient is an elderly resident of San Fernando Valley who became ill in late August.

Los Angeles County map/Thadius856
Los Angeles County map/Thadius856

This is the first SLEV case in the state this year. One mosquito sample from Playa Vista has tested positive for the virus this year.

“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 Muntu Davis, MD, MPH, Los Angeles County 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.”

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Saint Louis encephalitis virus is similar to West Nile virus and can affect the nervous system and result in infections of the brain, paralysis and cause death. While all county residents are at risk for Saint Louis encephalitis, the majority of people infected with Saint Louis encephalitis virus have no or mild symptoms. People over 50 years of age or individuals with lowered immune systems are at greater risk of experiencing severe symptoms when infected. Symptoms of severe disease include fever, headache, stiff neck, confusion and decreased alertness. There is no vaccine to prevent Saint Louis encephalitis, and only supportive treatment is available. Anyone with symptoms should contact their health care provider.