Tulare County Public Health has confirmed a human case of St. Louis Encephalitis, SLEV, in a Tulare County resident.

An additional five cases are currently under investigation and may result in the illness being SLEV or West Nile Virus. Public health officials urge residents to take precautions against mosquito bites, as mosquito samples positive for West Nile Virus have been detected in multiple locations within the county.

In addition, this case indicates that St. Louis Encephalitis Virus (SLEV) is also present, posing a risk to the public. The two viruses are similar and are transmitted by the same types of mosquitoes.

“Due to this increased activity and these reported cases, we strongly encourage residents to use safeguards to reduce their risk of contracting both West Nile Virus and SLEV through mosquito bites,” stated Tulare County Public Health Officer Dr. Karen Haught.


The Centers for Disease Control and Prevention stated the West Nile Virus is transmitted to humans by mosquitoes, and there's no vaccine or medication to treat the virus. Most people infected with West Nile will have no symptoms.

But about 1 in 5 people will develop a fever with other symptoms from 2 to 14 days after being infected. Severe cases of West Nile Virus can affect the central nervous system, resulting in meningitis and/or encephalitis, and can result in death or long-term disability.

The St. Louis Encephalitis Virus is in the same virus family as West Nile Virus. Both viruses are transmitted to humans when bitten by an infected mosquito.

Most people infected with SLEV will have few to no symptoms. The most common symptoms are mild, flu-like symptoms, including fever and headache, from 5 to 15 days after being infected. Like West Nile Virus, severe cases of SLEV can also affect the central nervous system, resulting in meningitis and/or encephalitis, and can result in death or long-term disability.

Residents are urged to increase their awareness of potential breeding grounds around their properties. Be on the lookout for homes that are unoccupied, since they may have swimming pools or backyard ponds that are breeding grounds for mosquitoes. It's recommended residents take the following precautions to avoid being bitten, thereby reducing their risk for exposure to both West Nile Virus and SLEV:

Use EPA-registered insect repellent such as DEET. Always follow label instructions carefully; Dress in long sleeves and pants during dawn and dusk or in areas where mosquitoes are active; Drain standing water that may produce mosquitoes; and Repair or replace door and window screens that have tears or holes.

Those who see areas of standing water that may be a breeding area for mosquitoes should contact their local mosquito abatement district. Those in South Tulare County can contact the Delano Mosquito Abatement District,(661) 725-3114 or online at: https://delanomosquito.com/.

Horses are also particularly susceptible to infection with West Nile Virus, but there's a vaccine for horses to prevent these diseases, and horse owners should have their horses vaccinated annually and keep vaccinations up to date as a preventive measure. For more information, visit the California West Nile website at http://westnile.ca.gov/.


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