SAN JOSE, Calif. (AP) — Santa Clara County has seen a sharp jump in birds infected with West Nile virus, which has prompted an increase in mosquito spraying that upsets many residents.

Santa Clara County, which includes San Jose, recorded 286 infected birds as of July 3, compared with only a handful at this time last year, according to the San Jose Mercury News. The county has already logged more than three times the number of cases found in all of 2013, and it accounts for nearly 60 percent of cases statewide.

“We’re seeing more than in all the other years,” said Mike Stephenson, the disease surveillance specialist with Santa Clara County Vector Control. “We’ve had other busy years, but not like this.”

Officials say the drought may be contributing to the increase in West Nile cases because birds and mosquitoes are coming into closer contact around a smaller number of watering holes.

In response, Santa Clara County officials have increased chemical fogging to kill mosquitoes that carry West Nile virus, which can be deadly for birds and humans.

Santa Clara County has already fogged 10 times this year, compared with 13 in all of 2013. Neighboring counties have had far fewer cases and foggings this year.

More residents are complaining about the increased fogging from truck-mounted misters that spray neighborhoods at night. They’re worried about the potential harmful effects of the pesticides.

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

County vector manager Russ Parman says pyrethroid, the pesticide used in the fogging operations, has been extensively studied and there haven’t been any documented cases of anyone being harmed in 30 years.

“It’s not known for knocking out anything bigger than a housefly,” county vector manager Russ Parman said. “We know more about these products going out than we do of what’s sold over the counter as herbal remedies.”

Since West Nile appeared in California in 2003, there have been more than 4,000 documented cases in humans statewide and 145 fatalities.

But officials say the vast majority of cases are unreported. Many infected people just think that had a bad case of the flu and didn’t get tested.

“Even its mild form averages 16 days off work,” Parman said. “It’s a very significant disease.”