ROSEVILLE, Calif., August 30, 2012 – The number of West Nile virus-positive birds in Placer County this year is triple that of last year, positive mosquito samples have more than doubled, and the season isn’t even over yet, reports the Placer Mosquito and Vector Control District.  Last year, the number of infected dead birds totaled 10 at the end of the season, this year the number is 33 so far, with more dead birds being reported and tested every day.  There were 48 positive mosquito samples last year, while this year’s tally is already at 101.

The newly reported human cases support the district’s data that there is a lot of virus activity in the western part of the county.  “Mosquito abundance is not unusual for this time of year. What we are seeing is a larger percentage of those mosquitoes infected with West Nile virus,” stated Dr. Mary Sorensen, entomologist and laboratory director for the district.  In fact, according to the Centers for Disease Control and Prevention, this is the worst year for West Nile virus since it was introduced to the United States in 1999.

Residents are encouraged to implement protective measures if they are planning to be outdoors around dawn and dusk during peak mosquito feeding activity this holiday weekend and throughout the early fall. “We have heard of some youth sports organizations implementing a mosquito repellent policy for activities that are scheduled during the dusk and early evening hours,” reported Joel Buettner, general manager for the district.  “We certainly support that message and encourage other outdoor recreational organizations to adopt similar policies,” he adds.  In addition to the district’s ongoing activities to control for immature and adult mosquitoes, Buettner also stated that the district is willing to assist youth and outdoor recreational organizations in implementing their repellent policies.

The district has scheduled ground-based adult mosquito treatments in areas of Sheridan, Lincoln, and Roseville for Friday morning, and aerial treatments over agricultural areas in the western part of the county on Friday and Saturday evening.  More information about the treatments can be found on the district’s website,

The Placer Mosquito and Vector Control District advises the public to implement the 3 Ds of protection:

  • Drain any standing water that may produce mosquitoes.
  • Defend yourself and your home by using an effective insect repellent and dressing protectively when outside, and making sure screens on doors and windows are in good condition.
  • Contact the District for any additional help controlling mosquitoes around your home.

For more information, contact the Placer Mosquito and Vector Control District at (888) 768-2343 or visit

2012 Placer County West Nile virus activity update: 33 dead birds, 4 sentinel chickens, 101 mosquito samples, and 3 humans have tested positive for West Nile Virus to date