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August 17, 2020

West Nile Virus Detected in Multiple SLCo Mosquito Pools

Nicholas Rupp - Email

(SALT LAKE COUNTY)—The Salt Lake County Health Department (SLCoHD) announced today that West Nile virus (WNV) has been detected in multiple mosquito pools* within Salt Lake County boundaries. Public health officials are urging residents to take precautionary measures to avoid exposure to the virus.

Local Mosquito Abatement Districts (MADs) have been trapping and collecting mosquito samples at numerous locations throughout Salt Lake County.

“We currently do not have any confirmed human cases of West Nile virus reported in Salt Lake County, but this is a good reminder that it is now especially important that residents protect themselves from mosquito bites, particularly in the hours from dusk to dawn,” explained Dr. Dagmar Vitek, SLCoHD medical director.

Although only some mosquitoes carry WNV, there is no way for residents to tell which mosquitoes may be infected so it is important to minimize exposure opportunities during mosquito season:

  • Use an EPA-registered mosquito repellent with DEET, permethrin, picaridin, IR3535 or oil of lemon eucalyptus; follow package directions about application.
  • Drain standing water in yards (old tires, potted plant trays, pet dishes, toys, buckets, etc.).
  • Wear long sleeves and pants after dusk.
  • Keep roof gutters clear of debris.
  • Clean swimming pools often or drain them.
  • Clean and stock garden ponds with mosquito-eating fish or mosquito dunks.
  • Make sure doors and window screens are in good condition so that mosquitoes cannot get indoors.
  • Keep weeds and tall grass cut short; adult mosquitoes look for these shady places to rest during the hot daylight hours.

WNV can cause mild to severe illness and many people may not even know they have been infected. It is estimated that less than 1% of people infected with WNV will develop neuroinvasive disease, which can result in debilitating long-term complications or death. Symptoms of WNV infection appear within 2 to 14 days of exposure and include fever, headache and body aches. More severe infections may include high fever, neck stiffness, disorientation, coma, tremors and muscle weakness or convulsions.

People over age 50 and people with weakened immune systems are at the highest risk of illness due to WNV, but anyone can become ill from the bite of an infected mosquito. WNV is not transmissible from person to person.

There is no specific treatment for WNV infection other than to treat symptoms. If you think you have WNV infection, contact your health care provider.

WNV was first detected in the U.S. in 1999 and in Utah in 2003. Last year, public health officials confirmed that 21 people in the state contracted the virus; 12 of those people developed neuroinvasive disease and 1 passed away. Because only 20–30% of infected people will have any symptoms at all—and many of those will notice only minor, flu-like symptoms—it’s likely that infection with WNV is more prevalent than the reported case numbers indicate.

*"Mosquito pool" is the term used for a group of mosquitoes caught and tested out of a single trap; it is not related to swimming pools or other bodies of water.