West Nile Virus activity increasing in Placer County

AUBURN, CALIF. – Placer County health and mosquito abatement officials are reminding residents and visitors to remain diligent about avoiding West Nile Virus, which is spread by the bite of an infected mosquito. Three new human cases have been recorded in the County, bringing the 2006 total to four. Additionally, west county rice fields will be harvested over the next several weeks, which may lead to increased mosquito activity.

“Historically, we see the most West Nile virus activity in the late summer and early fall,” said Dr. Michael Mulligan, Assistant County Health Officer. “With the long holiday weekend before us, we want to remind all residents and visitors to take simple, common-sense precautions to protect themselves from the mosquitoes that carry the virus.”

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The four cases this year have been in:

• Roseville, in the 95678 zip code, diagnosis confirmed Aug. 31;
• Rocklin, in the 95677 zip code, diagnosis confirmed on Aug. 28;
• Roseville 95661, diagnosis confirmed on Aug. 17; and
• Newcastle, in the 95658 zip code, diagnosis confirmed on Aug. 14.

“We’ve found West Nile virus in mosquitoes, dead birds, and sentinel chickens in Placer County this summer.  And we’ve had human cases, as well,” said Jamesina J. Scott, Ph. D., vector ecologist for the Placer Mosquito Abatement District. “We know that the virus is here, and we want to encourage residents to protect themselves from mosquito bites by wearing long-sleeved shirts and pants, using insect repellant, and when possible avoid being outside at dusk and dawn when mosquitoes are most active.”

In addition to the three human cases this year, there have been three sentinel chicken flocks that have tested positive for WNV; 17 mosquito pools have tested positive for the virus; and nine dead birds have tested positive for WNV. No horses have tested positive for the virus this year.

Most people who get West Nile virus from infected mosquitoes won’t become ill.  But about 20 percent may experience mild-to-moderate flu-like symptoms 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.  In California last year, there were 935 human cases.

The Placer Mosquito Abatement District and Placer County Health and Human Services offer the following additional reminders to prevent 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, flower pots and bird baths.
• Avoid mosquito bites by staying indoors at dusk and dawn when mosquitoes are most active, wearing long sleeves and long pants, and using an insect repellant that contains DEET or oil of lemon eucalyptus.
• Dead birds that test positive for West Nile virus are a surveillance tool to help track the disease.  If you find a dead bird, please call the state at 1-877-WNV-BIRD (1-877-968-2473) to report it, or do so online at www.westnile.ca.gov. 
• Horses are vulnerable to West Nile virus, and many die.  Contact your veterinarian about protective immunizations. West Nile does not spread between humans and horses.

If residents of Placer County have questions about West Nile virus or mosquitoes, are having mosquito problems, or need mosquito fish, they should call us at the Placer Mosquito Abatement District at 916-435-2140.