Map courtesy
Map courtesy

August 10, 2016 – West Nile Virus (WNV) was detected in a dead bird from Penn Valley this week. This is the first confirmation of WNV in the county this year. As of August 5, 2016, California has reported 10 human cases of WNV from eight counties and dead birds and mosquito samples have tested positive in more than 25 counties, which is above average for this time of year. So far in 2016, there have been no reports of human cases in our county but it is important to avoid mosquito bites.

It is possible the ongoing drought contributed to increased WNV activity as birds and mosquitoes may have had closer contact with more limited sources of water. Stagnant water is the perfect breeding ground for mosquitoes, be sure to eliminate any sources of pooling or collecting water around the home.

For most people, the risk of serious illness is low; however, some people (less than one percent) can develop a serious neurologic illness such as meningitis or encephalitis (brain inflammation). People 50 years of age or older have the greatest risk of complications.

To reduce the risk of being infected, residents are encouraged to:

  • Remain indoors at dawn and dusk when mosquitos are most active, or

  • Wear long sleeves and pants during dusk and dawn

  • Use a mosquito repellant containing DEET, Picaridin, oil of eucalyptus, or IR3535 as active ingredients before going outdoors. Check the label instructions to see which product is right for you.

  • Remove water standing for more than 3 days from bird baths, pet dishes, flower pots, outdoor stored automotive tires or neglected swimming pools.

California’s WNV website ( includes the latest information on WNV activity in the state. Californians are encouraged to report all dead birds through the website. Dead birds can also be reported by calling toll-free 1-877-WNV-BIRD (968-2473).

Zika virus is typically carried by a different mosquito than WNV, and that mosquito has not been found in Nevada County. There have been no confirmed cases of Zika virus in the county. Zika virus is associated with birth defects, and travelers, particularly those who are pregnant or planning to be parents, should consult with their physicians prior to travel to countries with Zika transmission.

Additional information for contacting Nevada County Vector Control can be found at:

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