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As California’s climate heats up, Valley fever spikes — especially on Central Coast

On a windy summer day a decade and a half ago, insidious fungal spores, each a tiny fraction of the width of a human hair, wafted through a Modesto orchard and into Jaime Gonzalez’s lungs.

Several weeks later, Gonzalez grew weak and feverish. The spores had infected him with Valley fever, a little-known and often-misunderstood disease that causes him fatigue, chronic pain and skin ulcers to this day. Sometimes, he said, his legs fail him.

“I try not to move from where I’m at because my feet will start to kill me,” said Gonzalez, 48.

Amid a deepening climate crisis, rates of Valley fever will likely rise as hotter, drier conditions plague the state, according to a recent UC Berkeley study. And there is concern that wet weather following long dry periods – the pattern California has experienced in recent weeks – may trigger the disease to spread even more.

Valley fever occurs when a person inhales spores of the soil-borne Coccidioides fungus. People who live and work around dry earth — farmers, construction workers, firefighters, archeologists and Central Valley prisoners — face the greatest risk.

Jaime Gonzalez, 48, of Modesto, is photographed in front of an almond orchard in Modesto, Calif., on Thursday, Jan. 19, 2023. A decade and a half ago, as Gonzalez walked out of a Modesto hospital after a month of treatment for a blood clot, a dust storm kicked up, wafting fungal spores into his lungs, giving him Valley fever. Gonzalez uses a cane to help him walk after suffering his 14th blood clot since getting Valley Fever. He also suffers from balance issues and is immune compromised. (Jose Carlos Fajardo/Bay Area News Group)
Jaime Gonzalez says he never heard of Valley fever when he contracted it a decade and a half ago. Neither did his late father, a farmer who was at greater risk of catching it than most Central Valley residents. (Jose Carlos Fajardo/Bay Area News Group)

But even among those groups, the disease is often unknown. Gonzalez’s father, a farmer, had never heard of the disease until his son, then a judicial assistant, contracted it in 2008.

The disease can linger for years, has no vaccine and disproportionately impacts people of color. While infections remain highest in the San Joaquin Valley, they’re now rising fastest along the Central Coast — especially as droughts come to an end.

Monterey County, for example, recorded seven cases of Valley fever per 100,000 people in 2008. The figure has trended upward since then, settling at 35 per 100,000 in 2021 — a five-fold increase in 13 years.

That’s low compared with inland counties like Kern, which reached 382 cases per 100,000 in 2019. But researchers say the coastal increase is accelerating and boosting the statewide statistics: California cases tripled from 2014 to 2018.

Roughly 40% of patients develop symptoms, which usually persist for weeks or months before fading. These can include fever, cough, fatigue, sweats, and joint or muscle pain.

In 1% of patients, the fungus spreads to the skin, bones or joints, as it did in Gonzalez’s case. In the worst scenarios, it reaches the brain and spinal cord, inflaming the membranes surrounding them.

Gonzalez didn’t get Valley fever from another person — the disease isn’t contagious — but from a dust storm that kicked up as he walked out of a Modesto hospital after a month of treatment for a blood clot.

Heat and dryness fracture the fungus, releasing microscopic spores into the soil. The wind then lofts them away, sometimes over the ocean. Sea otters and dolphins can get Valley fever as well.

The climate crisis has made hot, arid conditions more widespread. Though still most prevalent in a region that stretches from Arizona to the San Joaquin Valley, cases started popping up in southeast Washington state in 2010. Research indicates that by the turn of the next century, the disease could cross the Canadian border and spread east to the Dakotas.

The fungus can’t survive on heat and drought alone. It also needs water.

“Where soil moisture is low, the fungus is not able to grow as effectively,” said Jennifer Head, an environmental health researcher at UC Berkeley and lead author of the recent study.

So when a drought ends, the fungus’ growth surges, priming it to release more spores once hot, dry conditions resume. “We expect to see a spike in Valley fever cases at the end of the drought we’re in now,” Head said.

Head’s team analyzed climate data and records of over 81,000 Valley fever cases in California from 2000 to 2020, along with models of how many cases would have occurred without drought. The researchers found that from April 2016 to March 2018, after the state’s last major drought ended, California recorded almost 2,650 more cases than normal — more than offsetting the hampering effect the drought had on the fungus’s growth.

The fungus’s need for both drought and moisture explains why some coastal counties report the sharpest case spikes. In parched inland soils, the fungus releases spores easily but grows slowly. California’s coast, meanwhile, offers sufficient soil moisture — and now, because of climate change, more frequent dry heat as well.

As the disease ramps up, people of color bear the greatest risk of severe infection — even after accounting for occupation, said Dr. David Stevens, president of the California Institute of Medical Research in San Jose. The most vulnerable are people of Filipino ancestry, for whom the fungus is 175 times more likely to spread beyond the lungs compared to white patients.

Jaime Gonzalez, 48, of Modesto, is photographed in front of a walnut orchard in Modesto, Calif., on Thursday, Jan. 19, 2023. A decade and a half ago, as Gonzalez walked out of a Modesto hospital after a month of treatment for a blood clot, a dust storm kicked up, wafting fungal spores into his lungs, giving him Valley fever. Gonzalez uses a cane to help him walk after suffering his 14th blood clot since getting Valley Fever. He also suffers from balance issues and is immune compromised. (Jose Carlos Fajardo/Bay Area News Group)
Jaime Gonzalez, 48, stands in a Modesto walnut orchard. In 2008, he was infected with Valley fever as he was walking out of a hospital after a monthlong stay to treat a blood clot. (Jose Carlos Fajardo/Bay Area News Group)

Medical professionals haven’t figured out why. “That’s the 64,000-dollar question,” Stevens said.

Because early symptoms resemble bacterial or viral pneumonia, diagnosis often lags, giving the fungus time to get established.

Once diagnosed, patients typically take oral antifungal medications, though some cases require other methods.

Stephanie, an East Bay teacher and patient who asked that her last name not be used, also contracted Valley fever in a Modesto dust storm. The fungus reached her brain and spinal cord — at one point leading to two strokes in one night. Her medications were injected into her spinal canal. The powerful doses numbed her feet, making walking difficult.

She recovered enough to run her first half-marathon in 2018. But such recovery is rare, and she still takes medication to prevent a relapse.

“The drugs are getting better all the time,” said Stevens, who has worked with Valley fever patients for half a century. But, he added, “It’s not perfect.”

One reason no vaccine exists is that most vaccine research targets bacterial and viral infections, not fungal ones. The main hurdle, Stevens said, is that Valley fever still doesn’t affect enough people for vaccine development to be lucrative for pharmaceutical companies. As the disease spreads, that may change but any vaccine is still years away.

Gonzales, despite his chronic pain, regularly visits groups of migrant workers to explain the risk of Valley fever and promote prevention strategies, which include wearing N95 respirators and wetting soils before work.

“I push myself. I really do,” Gonzalez said. “I’m not giving up.”


Source: Orange County Register

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