West Nile virus: Many people will be infected, says health official West Nile virus: Many people will be infected, says health official (April 13, 2005)

** Infected bird found in Hillsborough.

By Marion Softky

Almanac Staff Writer

It's wake-up time for West Nile virus in San Mateo County.

The March 24 discovery in Hillsborough of a small bird -- a pine siskin -- infected with West Nile virus alerted health authorities that the sometimes-lethal disease is likely spreading in San Mateo County.

Last year the county discovered 17 infected birds, although there were no reported cases of West Nile virus in humans or horses.

Last week, Dr. Scott Morrow, San Mateo County's health officer, said he expects that many people in the county will come down with the virus, based on the experience of other regions where the virus has spread.

"There is a well-established pattern in which dead birds and mosquitoes infected with the virus precede reports of human illness," Dr. Morrow warned. "The Health Department urges residents to take steps now to protect themselves against mosquitoes."

Last year, there were a total of 830 cases of West Nile virus in California, primarily in Southern California; 28 people died from the disease.

The virus, which has been migrating slowly across the country, is passed primarily between birds by mosquitoes. Humans, horses and other animals bitten by infected mosquitoes can contract the disease.

While the virus is still rare, anyone experiencing symptoms of high fever, severe headache, and stiff neck should see a doctor, health authorities advise.

And since horses are particularly susceptible, horse owners should make sure their animals are vaccinated.

"Without vaccination, about 50 percent of horses with West Nile virus die," said Chindi Peavey, vector ecologist with the San Mateo County Mosquito Abatement District.
Counter-measures

West Nile virus is appearing earlier this year; last year, the first positive test was obtained at the end of July, Dr. Peavey said. Since last year's positive tests were scattered throughout the county, "we assume the virus is scattered throughout the county," she said.

With a staff of 17, the Mosquito Abatement District, which recently expanded to cover all of the county, makes regular inspections, treats mosquito-infected areas, provides free mosquito fish to residents with ponds, and responds to complaints.

It does not use insecticides, Dr. Peavey noted; it applies biological controls based on bacteria and hormones specific to mosquitoes. "If people have mosquito problems, call us," she said.

Just last week, the district deployed flocks of "sentry chickens" to four locations in the county, where they can be routinely tested for the virus. Flocks are located in San Bruno, East Palo Alto, the Webb Ranch near Ladera, and near Searsville Lake.

The district is looking for someone on the Coastside with a chicken coop to keep another flock. The district provides the chickens and the feed, Dr. Peavey said. "They can keep the eggs."

Crows, jays and ravens are particularly susceptible to West Nile virus, Dr. Peavey said. People finding freshly dead birds, including song birds, should keep them, and report them to the state online at westnile.ca.gov, or by phone to 877-WNV-BIRD (877-968-2473).
Prevention

To reduce risk of infection, health authorities advise:

** Drain standing water weekly, including from tires, cans, flowerpots and clogged rain gutters.

** Limit outdoor activities at dusk and dawn, when mosquitoes are most active, or dress in long sleeves and pants.

** Use insect repellants containing DEET; always follow label instructions carefully.

** Replace damaged or missing screens on windows and doors.

Anyone with mosquito problems or questions can contact the San Mateo County Mosquito Abatement District at 344-8592, or check online at smcmad.org.

More information on West Nile virus is available at the following Web sites:

** San Mateo County Health Department: smhealth.org/fightthebite.

** State of California: westnile.ca.gov.

** Centers for Disease Control and Prevention: www.cdc.gov.

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