Mosquito fighters in the Northern San Joaquin Valley have been preparing for the mosquito-borne West Nile virus for more than a year.

Now they are ready to lock and load for battle, with the potentially fatal virus's official arrival in California -- confirmed Wednesday in Imperial County in Southern California.

"The virus could already be here and under our radar screen," Allan Inman, manager of the Merced County Mosquito Abatement District, said Thursday. "I thought it would have been here in July."

In Merced, Stanislaus and San Joaquin counties, workers are checking flocks of "sentinel chickens" that are used to detect mosquito-borne sicknesses. Also, mosquitoes are being ground up -- in samples called pools -- and tested for West Nile.

And bird populations are being watched, because when the West Nile virus strikes, crows and jays are some of the first victims.

"We're getting ready for it, whether it be human cases or in the mosquito population," said Aaron Devencenzi, community education specialist for the San Joaquin Mosquito and Vector Control District.

West Nile virus was discovered in the United States in 1999, first in New York. It has since spread to 43 other states.

Last year, the government tallied 4,156 reported human cases of the virus and 284 deaths. This year's numbers are 599 cases and 11 deaths, according to the Centers for Disease Control and Prevention.

There is no vaccine as of now to protect people, nor is there a cure.

"There is no special treatment you can give to a person who is infected, the way an antibiotic would eradicate a bacteria," said Dr. Timothy Livermore, public health officer for Merced County. "It's up to their body's immune system to overcome the virus."

The good news is that most people bitten by mosquitoes with West Nile virus will not get infected. The CDC estimates that only two out of 10 people bitten will even get sick, usually with mild, flulike symptoms.

Vaccine is in the works

West Nile is fatal in less than 1 percent of all cases, said David Jones of the Stanislaus County Health Services Agency.

He said the CDC announced Thursday that a vaccine for people will be ready for testing by the end of the year.

Stanislaus, Merced and San Joaquin counties have signed on to a mutual aid pact to help one another if an outbreak occurs, said Lloyd Douglass of the Eastside Mosquito Abatement District in Stanislaus County.

Like other districts, Douglass' staff has been working on eliminating mosquito breeding grounds.

"A lot of people forget how much they can do for themselves," he said. "Until it gets here, people don't think much about it."

Any container of untreated water can become a breeding ground. For some mosquitoes, the time from birth to maturity is as short as four days.

Merced County bought a twin-engine airplane last year to combat the virus and is the only place in the state to have a federal waiver to spray populated areas, Inman said.

"That is a worst-case scenario," Inman said. "It would only take place if an outbreak of West Nile virus takes place."

Inman said the county needs the air power because "we have a unique blend of breeding habitat."

Along with breeding in backyard birdbaths and other stagnant water, the house mosquito, Culex pipiens, likes breeding in the lagoons found on the county's 300 dairies.

The creature known as the encephalitis mosquito, Culex taralis, prefers breeding in wetlands and rice fields. Merced County has more than 100,000 acres of wetlands and refuges that are being flooded now as part of the annual bird migration along the Pacific Flyway.

"The peak mosquito season usually starts now and extends into October," Inman said.

Health officials said simple measures can reduce exposure to the virus. People should stay indoors during dawn and dusk when mosquitoes are most active. And when outdoors, long-sleeved shirts and pants should be worn, and an insect repellant containing DEET used.

"They have to have DEET or they don't work," Livermore said. "Most of the time people get bitten by a mosquito, they aren't going to get infected by West Nile, but they do want to prevent those bites."

And Livermore added: Do not bank on rows of citronella candles to keep skeeters away. "I wouldn't suggest people buy citronella unless they like the way it smells," he said.

Anyone finding a dead bird without any signs of trauma is asked to call (877) WNVBIRD.

On the Net: Centers for Disease Control and Prevention www.cdc.gov Stanislaus County Health Services Agency www.hsahealth.org

Bee staff writer Mike Conway can be reached at 381-0208 or mconway@modbee.com.

Reprinted by permission of Modesto Bee.