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West Nile virus is targeted; fogging continues this week

By Monica Heger

The onset of summer brings more than just warm summer nights, barbecues and fun in the sun. The change of seasons also brings mosquitoes, some carrying the West Nile virus.

The Santa Clara County Vector Control District found the first West Nile virus-positive mosquitoes in West San Jose near Johnson Avenue and Prospect Road.

According to Kriss Costa, community resource specialist for the district, the findings came earlier in the summer than usual. She said mosquitoes don't usually start testing positive for the virus until late August or early September.

"All the water we had and the warm, humid weather really kicked off the mosquito activity," Costa said.

The district has been concerned about the growing threat of West Nile virus in Santa Clara County for some time. A mail-in ballot was sent to property owners last May, asking voters to approve a property-assessment hike. It passed, raising an additional $4 million annually.

Costa said the entire amount has gone toward thwarting West Nile.

"We predicted there would be a big increase with West Nile," Costa said. "We watched as it moved through the United States, so we knew it would take a lot more resources than it has in the past--more staff, products and outreach."

So far, she said the agency has found two groups of positive mosquitoes, both in the West San Jose area. The district has also found 14 dead birds in the county that have all tested positive for the virus.

"We'll be keeping an eye on the surrounding area," Costa said. "The way the virus moves, it looks like it came from the south area of Santa Clara County."

Costa advises residents to wear mosquito repellent, pants and long sleeves in the evening and to get rid of any standing water. She also said to inform the district of any mosquito problems, dead birds or standing water.

"We need to know where there are mosquito issues, and we need to know early," she said. "If we can take care of the mosquitoes in their aquatic stages, we're a lot better off than waiting until their adult stages."

Costa said dead crows, hawks or other birds could be an indication of West Nile, and residents should contact vector control. The area where the positive mosquitoes were found was fogged with Pyrenone 25-5, a chemical made from chrysanthemums. According to Dr. Noor Tietze with the vector control district, the chemical is not dangerous to humans.

The spraying was done July 7 from midnight to 3:30 a.m. because ultraviolet rays from the sun break the chemical down. The insecticide was sprayed as a thin mist from machines mounted in the back of county pick-up trucks. The area targeted for spraying encompassed Saratoga's Golden Triangle and parts of West San Jose.

Pyrenone is effective against mosquitoes because they lack the necessary enzymes to break down the molecule.

Tietze said Pyrenone is not the most commonly used spray for mosquitoes, but unlike other sprays, which target mosquito larvae, Pyrenone targets adult mosquitoes.

A community meeting was held July 5 in the Lynbrook High School gymnasium prior to the fogging to answer questions from concerned residents. There were more than 800 people at the meeting, Costa said.

"We were really happy. We liked seeing a response like that from the residents because it does mean they are aware of it and interested," she said.

Costa added they publicized the meeting through newspapers, radio and television, as well as 14,000 mailers, and then another round of 6,000 mailers. Yet, people still complained they hadn't been notified of the meeting.

Bill Blosen, who lives in the English Estates neighborhood, was on vacation while the meeting and fogging was taking place. However, he said it was valuable for residents in his community.

"I've noticed a significant decrease in the number of mosquitoes around my house," he said. "I had noticed them around the house, and they're not there anymore."

Blosen was especially concerned for his 3-year-old son, who likes to run around their back yard. The elderly and those with compromised immune systems are most at risk of catching the virus. Blosen said he's planning to keep an eye on the backyard to see if the mosquitoes return.

David LeDrew, who lives near the San Tomas waterway at Williams and Payne, didn't know if the fogging was done in his neighborhood, but said it made him a little nervous since he has two young children. LeDrew has been doing his part to stay vigilant and educated about the virus.

"I've been trying to clear the property of standing water and get rid of any area that would actually breed mosquitoes," he added.

Costa said the fogging went well, since there were almost no winds.

"The canopy of fog held," she said.

Traps were put out July 10 by vector control, and specimens were collected July 11. The results included the finding of three more infected groups of mosquitoes, rather than the 50 percent to 70 percent reduction rate they had hoped for, Costa said. They also found 10 infected swimming pools.

Costa added that especially with the hot weather over the July 7-9 weekend, the humidity factor gave a new population of mosquitoes the chance to quickly reach their adult stage.

As of press time, Costa said they are looking into hiring an airplane to conduct aerial surveys and find the source or sources that are causing the infected mosquitoes, and knock it out.

They'll be surveying a 5-square-mile radius and fogging again at the beginning of the week of July 17.

"When we have infected mosquitoes, the very day we don't fog is another day someone could get bitten," Costa said.

For more information about the West Nile virus, call 1.800.314.2427 or visit www.sccvector.org.

Lisa Sibley contributed to this story.