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County Resident Contracts West Nile Virus

September 01, 2010

AUBURN, CALIF. – A local Placer County resident became ill due to West Nile virus (WNV) infection earlier this month, marking the first reported human case in the county in 2010. The patient tested positive for WNV after a hospital visit. Confirmatory testing was then done by the California Department of Public Health laboratory.


The patient lives in Roseville, near an area where WNV has been detected in mosquito sampling this year. The Placer Mosquito and Vector Control District has done mosquito sprayings and fogging in the area, and continues to monitor this area and others in the county for the presence of WNV in mosquitos.

The patient, who has now recovered from the illness, regularly engages in outdoor activities and has no travel history to indicate the disease was contracted elsewhere.

So far this year, there have been 27 other counties in California where the disease has been detected and 26 other human cases. In 2009, there were no human cases reported in Placer County. In 2008, there were six.

“We’ve seen this same pattern for several years in California,” said Dr. Mark Starr, Placer County Director of Community Health and Clinics. “The disease first shows up in the southern part of the state and then is detected in Placer County in the latter part of the summer. Because West Nile infections are preventable, we strongly urge residents and visitors alike to take some simple precautions to avoid mosquito bites that can transmit the disease.”

Most people who are infected with West Nile virus will not become ill. However, for certain populations, the disease can cause serious illness and death. About 20 percent of those infected with WNV may experience mild to moderate flu-like symptoms, called West Nile fever, which may be prolonged. About one in 150 people will become very ill. People over 50 and people with suppressed or compromised immune systems are more likely to become seriously ill. West Nile virus is rare, but people with symptoms, including high fever, severe headache and stiff neck, should contact their health care provider immediately.

The Placer County Health and Human Services Department and the Placer Mosquito and Vector Control District offer the following reminders and information about preventing the spread of West Nile virus:

  • Drain standing water weekly, since that's where mosquitoes lay eggs. Check your yard for water in old tires, flowerpots and bird baths.
  • Avoid mosquito bites by staying indoors at dusk and dawn when mosquitoes are most active, and assure that your window screens are in good condition.
  • If you must be outdoors when mosquitoes are active, wear long sleeves and long pants, and use an insect repellant that contains DEET, picaridin or oil of lemon eucalyptus.
  • If you know of swimming pools that are not maintained and become “neglected” report them to the District at (916) 380-5444. These pools are ideal breeding grounds for mosquitoes.
  • Concerned residents may also request an inspection of a property or report a dead bird online through the District’s website: or by calling the District at (916) 380-5444.
  • As dead birds are a surveillance tool to help track West Nile virus, you are encouraged to report them by calling the California WNV hotline at 1-877-WNV-BIRD (1-877-968-2473), or online at
  • Horses are vulnerable to West Nile virus, and the mortality rate for unvaccinated horses is very high. Contact your veterinarian about protective immunizations. West Nile does not spread between humans and horses.

Placer County residents with questions about West Nile virus can call Placer County Community Health, or visit If residents have questions about mosquitoes, are having mosquito problems, or need mosquito fish, they should call the Placer Mosquito and Vector Control District or visit the District’s website at .