With this week's discovery that 11 more birds have died of West Nile virus in Butte County, it's definitely time to take precautions, said Dr. Mark Lundberg, the county health officer.

Five of the 11 birds came from the Chico area. Others came from Durham, Paradise, Magalia, Gridley and Oroville.

Starting Monday, the Butte County Mosquito and Vector Control District plans to begin spraying in some Chico neighborhoods, Lundberg said in a phone interview Friday.

He said it hadn't been decided exactly where the spraying would be done.

When that has been determined, the information will be posted on the Health Department's Web site: www.buttecounty.net/publichealth.

The spraying, known as "fogging," is done from slow-moving trucks that drive through neighborhoods. Officials say the spray, which kills mosquitoes, is harmless to humans and pets.

Lundberg said he's concerned that the number of West Nile cases in the north valley and around the state is substantially higher this year at this point than it was last year.

He said he hoped that reflects different weather patterns and doesn't signal that 2007 will be an especially bad year.

But clearly it's time to get serious about taking precautions against West Nile, he said.

That means using an effective mosquito repellent when you are outside in the early morning and evening and making sure there's no standing water, where mosquitoes can breed, around your house.

So far, there have been no human cases of West Nile in the county this year.

Glenn County reported its first human case of the year this week — a Hamilton City resident.

Statewide, there have been 27 human cases of the disease this year, 22 of them in Kern County. Last year at this time, just five human cases had been reported.

According to the Health Department, most people who get the virus will not become sick.

Others will have only mild symptoms, such as fever, headache and body aches. About one in 150 people become seriously ill with symptoms that may include a stiff neck, muscle weakness, vision loss, disorientation, convulsions, numbness or paralysis and coma. People over 50 are more likely to become sick and experience serious symptoms.

In Butte County last year, two people died from the virus.

West Nile is transmitted to humans and animals through the bite of infected mosquitoes.

The insects become infected when they feed on infected birds.

The Health Department offers these tips to prevent West Nile:

• Avoid spending time outside when mosquitoes are most active, especially at dawn and dusk.

• If outdoors at dusk or dawn, wear long pants and long-sleeved shirts, socks and shoes.

• Apply insect repellent before going outdoors with DEET, Picaridin, or oil of lemon eucalyptus.

• Make sure that doors and windows have tight-fitting screens. Repair or replace screens that have tears or holes.

• Drain standing water on your property that can support mosquito breeding (rain gutters, flower pot saucers, wading pools, etc.). Use mosquito fish (available from Butte County Mosquito and Vector Control) in water sources that cannot be drained, such as ponds and large water troughs.

• Contact the county mosquito control agency if there is a significant mosquito problem where you live or work.

While there is no evidence that people can get the virus from handling infected birds or squirrels, individuals should take precautions when disposing of them.

For more information on West Nile, including how to report and safely dispose of dead birds and tree squirrels, visit the state Web site at www.westnile.ca.gov or call 1-877-968-2473.