The key to avoiding a serious outbreak of the West Nile virus in Napa County is managing water to keep mosquitoes at bay.

"Do it now and have fewer bugs later," said Wesley Maffei, director of the county's Mosquito Abatement District, which has its headquarters in American Canyon.

Maffei updated the Napa County Board of Supervisors last week on the state of West Nile, noting the last serious mosquito-borne illness locally was encephalitis in 1995. "West Nile has become a much more serious issue," he said.

About 800 cases were reported in California last year, most resulting from the availability of standing water and other habitats that promote mosquito breeding.

According to the Centers for Disease Control and Prevention, all of the continental United States, with the exception of Washington state, has experienced West Nile virus. Most area have reported human cases, although some only find the virus in dead birds. California has far and away the greatest number of reported human cases.

Maffei said new privacy laws are thwarting eradication efforts to some extent. "People were open to letting the district do its job," he said, "but it's much different now."

Small amounts of standing water in a bird bath or other small container can affect an area of up to two square miles. "We're searching as best we can," said Maffei.

Several dead birds have tested positive locally, and although the peak of the season is in the fall, "We're already having experiences. It's earlier than ever."

Last year, there were reports of West Nile from Napa, Yountville and American Canyon. "They don't know political boundaries," said Maffei, noting Southern California has had most of the cases, but there has been a noticeable move to the north.

Most people who contract the West Nile virus show no visible signs of illness, but about 20 percent develop West Nile fever. Symptoms include fever, headache, fatigue, and occasionally skin rash, swollen lymph glands and eye pain.

In rare cases, West Nile develops into meningitis, encephalitis or polio-like disease. There have been deaths reported as a result of the virus.

Last year, the Napa County Civil Grand Jury recommended a concentrated public relations campaign to help fight the spread of the virus, but Maffei said his board of directors did not feel hiring a consultant to take on a PR campaign was fully justified.

"The grand jury didn't realize the full ramifications," he said. "We respond to all calls. You get a real person when you call us. None of this answering machine nonsense."

Maffei said Napa County has been recognized by the state for what it is doing to manage West Nile.

County Health officer Dr. Karen Smith said her department is coordinating efforts with local hospitals and helping to spread the word.

The Mosquito Abatement District encourages residents to:

* Examine trees on their property for holes or cavities that can hold water.

* Contact a tree surgeon or local nursery if holes are found to determine the best way to address the problem.

* Check and clean gutters that collect plant debris and trap water.

* Empty, turn upside down or throw away containers that collect water, such as cans, buckets and old tires.

* Use insect repellents when in an area where mosquitoes are found. Read and follow the directions carefully.

The Mosquito Abatement District was formed in 1925. It currently has a staff of seven full-time employees and one half-time worker. It is governed by a six-member board of directors with one from each municipality and one from the county.

The district derives the funding for its $1 million annual budget from property taxes and a special benefit assessment.

Napa County's Mosquito Abatement District will pick up dead birds in order to test them for West Nile virus. Call 553-9610 for help or information.