Utah's unseasonably cool and wet weather the past couple of weeks has delighted not only water managers and gardeners, but also the swarms of mosquitoes that carry West Nile virus.

The Utah Department of Health announced Thursday that five mosquito pools statewide have tested positive for West Nile — three in Salt Lake County, one in Washington County and one in Box Elder County. Residents are encouraged to take precautionary measures to avoid mosquitoes and to be aware of West Nile symptoms if they've been bitten.

JoDee Summers, a disease epidemiologist at the Utah Department of Health, said detection of the virus locally has occurred a littler earlier this year than in past years due to the weather. Summers said it could be one of the state's worst mosquito seasons in more than 20 years.

The health department has placed traps at strategic locations throughout the state — including one area around Salt Lake City International Airport — and mosquitoes are collected once a week, she said.

"They grind them up and test their blood" to determine whether West Nile is present in that particular area, Summers said.

The airport location was one of the three Salt Lake County pools that tested positive for the virus.

Though most people who become infected with West Nile don't experience any symptoms, about 20 percent will develop flu-like "body aches, fever, maybe a rash and fatigue — generally feeling crummy," she said.

The symptoms differ from the H1N1 flu virus because there is no respiratory involvement. West Nile doesn't create congestion, coughing or sneezing, Summers said.

A small percentage of people who experience symptoms may progress into a case of West Nile fever, which includes a severe headache and/or stiff neck.

"Those definitely require a doctor's care," she said.

Since 2003, there have been 318 confirmed human cases of West Nile in Utah — eight resulting in death — and predicting how many may occur this year is simply a guessing game, Summers said.

"Every year has been very different," she said. "The first year we had one, then 12, then well over 170 cases, then back down to 80. And last year we had under 30 cases, so we have no idea what each year is going to bring."

Residents can help deter mosquito breeding by eliminating any pools of standing water, including empty flower pots, old tires or wheelbarrows.

"Mosquitoes can breed a lot of larva in very small amount of water," Summers said.

To avoid mosquito bites:

 Use repellent containing DEET or Picaridin while outdoors.

 Wear long-sleeved shirts and pants while outdoors.

More information: www.health.utah.gov/wnv or 801-538-6191.

E-MAIL: carrie@desnews.com