PROVO — West Nile virus has been detected in two additional mosquito pools in north and central Utah County and in a sentinel chicken from Duchesne County, health officials said Monday.

The virus has now been found in four counties: Duchesne, Salt Lake, Utah and Washington.

"Mosquitos trapped on July 3 have come back from the Utah Public Health Laboratory as being positive from the Lehi and south Provo areas," said Bob Mower, mosquito abatement division director for the Utah Public Health Laboratory. "This is in addition to mosquitos found on the south end of the county (in June)."

So far, the virus has been confirmed in sentinel chickens, wild birds and mosquito pools. No human infection has been reported.

"But it just reminds us to take precautions to protect ourselves and our families," Mower said.

Additional ground spraying or fogging has been taking place since June, Mower said.

"We are also looking at doing some aerial spraying the end of this week in areas inaccessible to our fogging trucks," he said.

West Nile virus was first detected in Utah County on June 12, nearly six weeks earlier than in 2005.

"This early hot weather is probably why we have the virus detection so early this year," Mower said.

Though spraying helps reduce the number of mosquitos in an area, Utah County residents also can do their part to prevent spread of the virus, he said.

Prevention measures include:

• Avoiding outdoor activities such as gardening at dusk through dawn when mosquitoes are most active.

• Covering up by wearing long-sleeve shirts, pants, shoes and socks if outside during the periods when mosquitoes are most active.

• Using mosquito repellents with DEET, and correctly following product directions for children and how often it should be applied.

• Eliminating standing water in tires or similar water-holding containers, which may serve as mosquito breeding sites.

For information about West Nile virus or Utah County mosquito abatement efforts, visit www.utahcountyhealth.org or call 851-7637.