Climate Change is Spreading a Debilitating Fungal Disease Throughout the West

Valley fever, contracted by inhaling the cocci fungus that flourishes in Southwestern soils, is spiking on its home turf and migrating to new territories.

People with Valley Fever undergo treatment at San Joaquin Valley Pulmonary. Credit: Brian Vander Brug/Los Angeles Times via Getty Images
People with Valley Fever undergo treatment at San Joaquin Valley Pulmonary. Credit: Brian Vander Brug/Los Angeles Times via Getty Images

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When Tim Gulley moved to Bakersfield, California in the late 90s, his dad would order him inside when wind kicked up dust from the area’s vast agricultural lands. 

“Valley fever,” officially known as coccidioidomycosis, an infection caused by a soil-borne fungus, could come with the dust. 

Inhaling just one microscopic spore of the coccidioides fungus—cocci for short—can lead to a disease that kills around 200 people every year and leaves thousands of others struggling with fatigue, pneumonia, night sweats and headaches that can drag on for years. The spores can drift, invisible in the air, up to 75 miles from where the wind picks them up. 

Gulley hadn’t thought much about his dad’s warnings until about two months ago, when he started shivering uncontrollably and couldn’t catch his breath. At first, he thought it was Covid-19, particularly since he’s currently staying in a shelter, sharing space with several other men. But blood tests and X-rays discovered the 48-year-old had pneumonia caused by valley fever.

“No idea how I got it,” he said. “I’m inside most of the time.”


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Gulley doesn’t work in construction or farming, two occupations known to be at high risk for catching valley fever, but he lives in the San Joaquin Valley, for which valley fever is named and the home to an escalating number of cases. California has seen an 800 percent increase in cases in the last two decades. Infections are also steadily climbing in Arizona, the state with the largest number of infections. (Together, the two states account for 97 percent of valley fever cases.)

Climate change is largely to blame, creating ideal conditions for the coccidioides fungus to thrive and spread. Increasingly intense rains produce rapid fungal growth, and prolonged drought fragments the hairlike fungal strands into spores that easily disperse when soils dry out.

Morgan Gorris, an earth system scientist at Los Alamos National Laboratory who has been studying valley fever for seven years, recently modeled what the future of the disease may look like as the climate warms. Under a high greenhouse gas emissions scenario, she found the fungus would dramatically expand northward into areas where it has never been found before. “The endemic region for valley fever expands through the whole western United States and ends up touching the U.S. Canadian border,” she said.

An Explosion of Cases and Costs

Once a problem confined to the hot, dry Southwest, valley fever is popping up in regions once thought too cold or wet to host the fungus. In 2014, epidemiologists found cocci spores in eastern Washington after valley fever cases started emerging there a few years prior. 

Jennifer Head, a researcher at University of California, Berkeley specializing in epidemiology, recently completed a study detailing the nuanced relationship between cocci and weather patterns that are shifting due to climate change.

The arid southern San Joaquin Valley, for example, tends to see a “blooming of cases” when an intense wet year follows years of drought. In cooler, wetter areas, like the coastal regions of California, increasingly hot summers may be responsible for heightening the risk of valley fever. Those wetter regions of California, Head says, get plenty of rain to support fungal growth.

“What they might lack is the heat needed to dry the soil out and enable the spores to fragment and blow around,” she explained, adding that incidence rates seem to be “super sensitive to increases in temperature.” The northern San Joaquin Valley, which typically has fewer total cases than the southern valley, experienced a 1,500 percent increase in infections from 2000 to 2018.

valley fever

By the end of this century, Gorris predicts regions where the disease is endemic may expand to include millions more people, and the estimated number of people who will become sick may increase by 50 percent. “Not only is valley fever going to be detrimental to human health,” Gorris said, “it’s going to be quite costly.” 

According to the Centers for Disease Control and Prevention, about 20,000 cases of valley fever are reported each year. But scientists and doctors believe the number of people infected  is far higher, around 150,000 to 200,000 annually. Most cases are never reported or diagnosed because about 60 percent of patients who inhale cocci spores have no symptoms and never get tested. 

Of the 40 percent who become sick, just under half require hospitalization. To keep the disease at bay, patients take expensive antifungal medications for months, years or their entire lives, depending on the severity of the disease. Those drugs suppress the division and growth of the fungus, but do not kill it, and the disease is notorious for how long it can linger. 

“Even though it’s a small amount of people who get sick, they get very sick and use a huge amount of health resources,” said Dr. Royce Johnson, medical director of the Valley Fever Institute in Bakersfield, a clinic that opened in 2015 with the goal of better understanding the disease and treating the growing number of infected people. 

In roughly 1 percent of cases, the inhaled spore turns into a tiny spherule that rapidly divides within itself until it bursts, releasing hundreds of particles that not only attack lung tissue, but enter into the bloodstream and are carried to other parts of the body, including spinal fluid and the brain. That can lead to meningitis. The disease can also spread to skin and even bone, occasionally forcing doctors to perform amputations. That reproduction and release will repeat every few days. 

For a disease that most of the country has never even heard of, the estimated economic burden of valley fever totals a whopping $1.5 billion every year. If Gorris’s projections are correct, that number could skyrocket to $18.5 billion by the end of the century. 

Often Misdiagnosed Threat to Farmworkers, Firefighters and Prison Inmates

Climate change is expected to fuel a wave of new vector-borne diseases, such as those spread by mosquitoes, as well as fungal pathogens that will sicken humans, but valley fever has actually been around for more than a century, infecting people in the western United States, Mexico and Central and South America. 

A 36-year-old soldier in Buenos Aires in the early 1890s was the first recorded case of coccidioidomycosis. He sought medical help for large ulcerating skin lesions on his face, another that resembled a cauliflower on his arm and recurrent fevers. (This patient’s head reportedly remains preserved in a jar of formaldehyde at the University of Buenos Aires.) A few years later, a manual laborer from the San Joaquin Valley died from a similar mystery illness and an autopsy revealed nodules on his lungs, spleen and other organs. Originally thought to be a parasitic infection, the cause of death was later identified as the fungus that leads to valley fever.

In California, farmworkers who spend entire days in dusty fields have a high risk for contracting valley fever. Those who disturb parched soil when picking root crops, such as beets and carrots, are particularly exposed. But other populations are also vulnerable because in the southern San Joaquin Valley, dust is like smog in Los Angeles—nearly impossible to escape. Outbreaks have occurred in prisons hemmed in by brown, arid landscapes; during construction of solar farms in open fields; and among wildland firefighters who inadvertently breathe in flecks of dirt while digging firelines. In 2019, California passed a law that required construction companies working in endemic areas to educate their employees about valley fever, and train them in preventive measures like wetting dirt before digging and wearing face masks. 

Older men and people with other health challenges, particularly diabetes, are at higher risk for severe illness, as are Black and Filipino people. The disease disproportionately affects Black people in Arizona and, in California, Black and Hispanic people, particularly Hispanic farmworkers, are more likely to contract valley fever than white people.  

While certain people are at heightened risk, the disease can strike anyone, said Dr. John Galgiani, who’s been studying it for 40 years and is the director of the Valley Fever Center for Excellence at the University of Arizona.

“If you get pneumonia in Arizona, around Phoenix or Tucson, it’s about a one chance out of three that it’s valley fever,” he said. “But many people incorrectly diagnose it as a bacterial infection.” In the San Joaquin Valley, about one in four pneumonia cases are caused by valley fever, according to infectious disease doctors in California. 

Patients who’ve inhaled cocci are often initially diagnosed with the flu, a sinus infection or bacterial pneumonia. Johnson, of the Valley Fever Institute, says that confusion is largely due to a lack of knowledge about the disease in the medical community, something he and others are trying to remedy. For a long time valley fever has been “a paragraph” that medical students read during medical school, he said. Unfortunately for infected patients, a delayed diagnosis combined with a weak immune system can lead to severe complications. 

Paul Ness, a retired 72-year-old who lives in suburban Phoenix, didn’t pay much attention to sudden piercing headaches in the fall of 2018. He’d never taken so much as an aspirin in his life because he rarely battled more than a mild cold. But when he started coughing up blood and sweating so badly at night he’d “soak the bed two or three times,” he went to a doctor who gave him antibiotics, thinking it was pneumonia. When he didn’t improve doctors performed a lung biopsy and diagnosed him with valley fever, and he was hospitalized for 13 days. 

Ness improved, but in the fall of 2020, fevers, headaches and weakness roared back. A spinal tap showed the fungus present in his spinal fluid and he learned that his infection had progressed to meningitis.

Today he’s on a twice-daily antifungal medicine, as well as a palm-full of other pills, but symptoms stubbornly persist. “I have headaches 24/7,” he said. Sometimes they feel “like an arrow shooting in my head,” while other days it’s more of a relentless throb on the left side, then the right.

There have been no new treatments approved for valley fever in the last 40 years, and no FDA-approved antifungal drugs exist for it. Instead, doctors prescribe antifungals that are approved for other maladies but also help to stop cocci from growing in the body. 

One of the antifungal medicines didn’t work for Ness, another made him feel awful. The one he’s on now costs him a little more than $1,400 every month until he reaches his maximum out of pocket cost of $6,700 under Medicare; then the price drops to $300.

“I keep a VISA card just for medicine,” he said on a recent morning. “I just looked at it and the balance for this month is $4,000. I don’t like to see that money go out the door but I can still pay for groceries. Fortunately I’m able to pay. I don’t know what I’d do if I couldn’t.”  

An avid golfer, Ness isn’t sure how or when he inhaled the spores, but he’s largely had to give up golf because he’s too weak to play.

“I know lots of guys who’ve had (valley fever). They get it, they take an antifungal for three months and they’re fine,” he said. “Mine didn’t (improve). I think it’s just the luck of the draw.”

Racing to Understand Rarely-Studied Fungal Infections

Part of the mystery surrounding valley fever is because fungal infections don’t get the attention of bacterial and viral infections.

“This is a really underfunded and understudied group of organisms with potential serious consequences.” said Bridget Barker, a researcher and professor at Northern Arizona University who studies the cocci fungus. “It’s been an uphill battle but I think we’re finally getting traction.” 

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The legislatures in both Arizona and California have increased funding for valley fever in recent years, and in February, the National Institutes of Health awarded $4.5 million in grants to researchers in both states to better understand the range of severity in valley fever and research a potential vaccine. (A vaccine for dogs, an animal prone to infection with the fungus, is already in development.)

Barker is among a small group of scientists trying to better understand how the coccidioides fungus operates. Why, for instance, can cocci turn up in one patch of soil but be totally absent from another a few feet away. How is it spreading into new territories? In eastern Washington, researchers believe the fungus may have been hanging around but dormant until conditions warmed. 

There’s less confidence about the cause of a recent, sudden explosion of cases in northern Arizona. Perhaps, Barker said, wind carried spores from Phoenix, where the fungus is widespread. “(Flagstaff) is only 200 kilometers from a source,” she said.

Using genotyping and air sampling, she hopes to identify various cocci strains that exist in the Southwest. A recent grant is also funding Barker’s research into better predicting seasonal risks of disease outbreaks. 

At the University of California, Berkeley, ongoing research is exploring how rodents that burrow into soil may play a role in valley fever. When the animals die, cocci spherules held in their lungs wind up back in the dirt, and the burrow can become a hotbed for fungal growth.  

Gorris, who continues to study fungal diseases, believes valley fever’s spread doesn’t have to prove as dire as her model projects. “When we looked at a moderate climate-warming scenario, we found that reducing greenhouse gas emissions would reduce the expansion of the Valley Fever endemic region,” she said. “Changes in the amount of greenhouse gas emissions changes the outcomes and the health effects of this disease.”