When three dead crows tested positive for mosquito-borne West Nile virus last week, Cheriel Jensen began to plot her escape.

Infected birds portend the start of pesticide fogging, which she blames for a host of ailments: rashes, watery eyes, dizziness, fatigue and a prevailing, progressive debility. To avoid the spraying, conducted several times a year by the Santa Clara County Vector Control District, Jensen often flies out of state or drives down the coast to wait it out from a distance.

“I can’t sit around here while they poison us,” says the 75-year-old retired county planner, who lives with her husband in Saratoga. Fed up with what she calls a chemical assault, Jensen lawyered up to sue the county and put a stop to it. Though a judge rejected the case on Friday, she plans to appeal the decision. “There’s too much at stake,” Jensen says. “They’re slowly, steadily sickening us.”

The lawsuit, filed in coordination with the nonprofit Healthy Alternatives to Pesticides, argues that the county needs to conduct an environmental review to warrant insecticide spraying. It also claims that the fogging unjustifiably encroaches on private property and kills other beneficial animals insects.

“It’s chemical trespass,” says Brandi Madison, a co-organizer of Healthier Alternatives to Pesticides. “You have a government agency putting poison on our private property without our consent, without any warrant.”

They accuse the county of sensationalizing the threat of West Nile disease to justify truck-mounted or aerial fogging. Chemicals used, they say, upend delicate ecosystems, killing fish, frogs, dragonflies, mosquito-eating bats and other wildlife while weakening human immune systems.

“This is absolutely excessive,” agrees Alexander Henson, the environmental lawyer

enlisted to work on the case. “You find one infected bird and you spray for miles around, killing all the bugs within that area. They downplay it, saying it won’t kill larger bugs, but right on the label you can read the warning saying it’s bad for bees. Something’s not right.”

County officials, however, say the group overstates the dangers of these pesticides and understates the risks of West Nile virus, a mosquito-borne pathogen that in people triggers flu-like symptoms, nerve damage and, in very rare cases, death.

“Any time that you put a pesticide into the environment, especially in urban areas, there’s going to be a group of people concerned about health,” Denise Bonilla, head of vector control, tells Metro. “That’s understandable and we’re trying our best to answer people’s questions, while also educating them about the risks if we don’t spray.”

While it’s unclear whether the lawsuit will move forward given its recent setback, simmering public distrust has prompted the county to step up outreach and education to keep panic from spreading. Especially when coming off the most intense West Nile Virus season to date, which kicked up a flurry of questions and complaints about fogging. Vector control went from spraying only a few times a year when it started about a decade ago to 19 times in 2014, when field workers identified 925 infected birds and 11 human cases.

“They’re spraying more, but reporting more cases of West Nile,” Keith Howe, another member of Jensen’s anti-fogging group, skeptically remarks. “More spraying, more West Nile, more everything. What does that tell you?”

Bonilla says the drought may be responsible for the growing rate of infection. Warmer temperatures shorten mosquito life spans, and thus their breeding and feeding cycles. A drier climate also forces animals to flock to fewer watering holes, further quickening the spread of the virus. “We had a crazy season last year,” Bonilla says. “We have had to spray more to keep it under control.”

The county uses a product called Zenivex, a pyrethroid insecticide that’s a “quick, permanent knockdown” for mosquitoes, gnats, midges and flies, according to the company’s label. The Environmental Protection Agency and the Centers for Disease Control and Prevention give the chemical manufactured by Zoecon the all-clear. But Jensen and others say public agencies have underestimated its cumulative environmental impact.

Bonilla says her office hears from more people requesting insecticide than refusing it because they worry about the spread of West Nile. In 2014, the county reported nine hospitalizations from mosquito-borne illness. Pyrethroids—a synthetic form of pyrethrins, a compound derived from chrysanthemums and often found in flea medication for cats and dogs—give the county a quick way to fight the virus. Warning labels point out that contact with the spray can cause nausea, numbness, wheezing and irritation to the eyes, ears and throat. Bonilla says it’s applied in doses low enough to render it imperceptible to most people, but acknowledged that people with acute sensitivity may feel the effects of it.

To assuage public backlash, county supervisors considered allowing people to opt out of spraying. But they dropped the idea after Bonilla told them last month that having foggers shut off at certain addresses would undermine the effectiveness of the program for everyone else. She noted that Orange County, which canceled a series of scheduled foggings last year, saw a historic surge in West Nile cases. Of the 282 people infected in the Southern California jurisdiction, eight died.

“The question is, what’s the bigger threat here? Pesticides or West Nile virus?” Madison posits. “In the entire state, with a population of 39 million people, only 29 died from West Nile related illness last year. That’s statistically insignificant. Meanwhile, everyone in our communities inhales the chemicals to fight it.”

Bonilla counters that even one life saved is worth the effort. Fatalities, she adds, would probably stack up if widespread spraying stopped altogether.

“When West Nile showed up, it was just something we had never seen here before,” Bonilla says. “It was completely different and spread so quickly across the United States, out-competing other viruses normally found in mosquitoes. We don’t really see those other viruses anymore. That’s why this was such a big deal. Not everyone had symptoms, but other people did feel sick and some people died.”

Though exempt from having to conduct an environmental review about pesticide use, the district voluntarily drafted a report detailing all the ways it controls mosquitoes and other disease-transmitting critters.

“We’re trying to be as transparent as possible,” says Bonilla, who assumed her role last fall. She says chemical fogging is a last resort, and the district delivers mosquitofish, free of charge to anyone who asks, to gobble up larva in ponds and pools. Field technicians will deploy mosquito-killing bacteria or pour a coconut oil film on standing water to suffocate floating larva.

“Over 99 percent of our time is spent larviciding,” says Bonilla, referring to methods targeting larval insects. “That’s what we do on a daily basis. We go out and inspect the marshes, people’s swimming pools, ponds, backyards. We look at physical conditions. We keep in mind people’s cultural practices. We tell people to dump and drain standing water. We see if they’re screens need repair. It really is an all-encompassing, integrative approach. In many ways, we already use alternative pesticides.”

The county also resorts to adulticiding—killing full-grown mosquitoes—when it finds West Nile Virus and other bird-hosted, skeeter-spread illnesses. County-employed disease hunters also keep tabs on outposts of cooped-up hens. Through routine blood tests on these so-called sentinel chickens, they can predict and prevent an outbreak.

When the county decides to spray, it alerts residents in targeted neighborhoods through robocalls, flyers and email. The notice advises people to stay indoors, close the windows, shut off fans, keep pets inside and cover pet food to avoid contamination. Beekeepers often relocate their hives or cover them in burlap to protect the colonies.

Beehives in Jensen’s front yard recently lost their queens, which she considers another side effect of spraying. She fears they won’t survive another spate of fogging, and she’s considering visiting a sister in Salt Lake City when that happens.

“I have to physically leave,” Jensen says, “ just get up and go as fast as I can.”