Santa Clara County Sees Surge in West Nile Virus Cases

A record number of West Nile Virus cases is causing some anxiety in Santa Clara County. 

As of July 3, there were 286 birds infected with the disease in Santa Clara, which represents three times the number of cases recorded last year.

Santa Clara County Vector Control surveillance specialist Mike Stephenson said there has been an increase in West Nile cases statewide, but the problem is particularly severe in Santa Clara County which accounts for nearly 60 percent of the cases.

One reason for the massive increase may be the state’s ongoing drought. According to county vector manager Russ Parman, the lack of rainfall has reduced the number of watering holes, placing birds and mosquitos in closer contact with each other. 

To alleviate the problem, the county has stepped up its fogging efforts. Santa Clara has already conducted 10 fogging operations, compared to 13 in all of last year.

The increase in mosquito control efforts now has many residents worried about the potential impacts on environmental health, however. 

"I'd like to know who is advising the county that spraying is worth it," said Sunnyvale nurse Jennifer Schmid. "This stuff is so toxic. Where's the cost-benefit risk analysis?"

Russ Parman assured concerned residents that fogging is relatively safe. Pyrethroid, which is the pesticide used during fogging operations, is a less toxic, synthetic version of a substance commonly found in flea shampoos. And, in the past 3 decades, there have no documented cases of it causing harm, Parman said. 

West Nile Virus first appeared in California in 2003. Since then, 4,000 human cases have been recorded, with 145 fatalities. Historically, Contra Costa County has seen the largest number of documented cases (47). Santa Clara has had 19 human cases.

Read more about the surge in Santa Clara West Nile cases here.