Valley fever, also known as coccidioidomycosis, is increasingly affecting people and animals across the arid regions of the western United States. The disease is caused by a fungus that lives in the soil, especially in California’s Central Valley and similar environments. When the ground is disturbed, tiny spores can become airborne and inhaled.
Rex Dangerfield, a 56-year-old resident of Stockton, California, recounted his experience with valley fever after being exposed while gardening in 2013. Within weeks he developed headaches and eventually was diagnosed with meningitis caused by the fungus. “I don’t feel normal anymore,” Dangerfield said through tears. “I used to be able to play basketball. I used to love to bowl. I can’t do that anymore.” He now requires lifelong antifungal treatment.
The symptoms of valley fever often resemble those of other respiratory illnesses such as pneumonia or common infections, which complicates diagnosis. Dr. George Thompson, an infectious disease physician who co-directs the UC Davis Center for Valley Fever at UC Davis Health, noted that patients are frequently misdiagnosed and treated unsuccessfully with antibiotics before the correct diagnosis is made. “Patients with uncomplicated respiratory disease are often given multiple courses of antibiotics erroneously, but eventually they feel better,” Thompson said. “They’re never diagnosed definitively or accurately.”
He advised: “If you’ve driven through the valley and you’ve got a cough or an illness that doesn’t seem to be going away for weeks or even a month, think about valley fever. You only have to breathe in one spore once to acquire the infection.”
In some cases, such as Dangerfield’s, the disease can invade organs beyond the lungs and require continuous medical intervention.
Another patient, Kyleigh Cooyar, described her prolonged struggle for a correct diagnosis after traveling through California’s Central Valley in 2015. She was initially misdiagnosed with Still’s disease before tests confirmed valley fever had spread to her ovaries. The initial antifungal treatment left her physically debilitated until she began care at UC Davis Health under Dr. Thompson’s supervision. “He’s the one that got it under control,” she said. “I think he saved my life.”
Valley fever also affects animals; dogs are particularly susceptible due to their tendency to dig in soil where fungal spores may reside. Dr. Jane Sykes of UC Davis explained: “I’ve had dogs that have been referred to me because they’ve been diagnosed with chronic kennel cough, when in fact they have valley fever.” In severe cases like Cooper—a boxer mix treated at UC Davis—surgery and ongoing antifungal therapy were necessary for recovery.
Researchers at UC Davis are collaborating across disciplines to improve detection and treatment strategies for both humans and animals affected by valley fever. Dogs are proving useful as sentinels; their patterns of infection help scientists map potential risks for human populations because dogs typically remain local and engage directly with contaminated soil.
Studies conducted by Sykes and colleagues analyzed nearly ten years of dog antibody tests nationwide and found nearly 38% were positive for valley fever exposure during this period. Mapping these results revealed significant overlap between canine and human cases in endemic states such as California and Arizona; new positive results have also appeared in states not previously recognized as high-risk areas.
The expanding range of valley fever has been linked by researchers to changing climate conditions—specifically cycles of heavy rain followed by droughts—which favor fungal growth and dispersal via dust storms or wildfire smoke.
Dr. Thompson highlighted recent findings indicating much higher actual case numbers than those officially reported: he co-authored research estimating up to 360,000 symptomatic cases occurred nationally in 2019—far exceeding current surveillance figures.
Treatment currently relies on antifungal medications which suppress but do not cure the infection; some patients require these drugs indefinitely. However, new therapies are under development showing promise against resistant fungal pathogens affecting both humans and animals.
Research collaborations involving samples from patients like Cooyar and Dangerfield aim to uncover genetic factors influencing susceptibility while supporting efforts toward developing effective vaccines—especially since a preventive vaccine for dogs may soon be available.
“We’re really at the pinnacle of science right now,” Thompson said. “We’re hoping to see some big breakthroughs and advances just over the next six months.”
As cases continue rising—in California alone nearly 12,500 were reported last year—efforts led by institutions such as UC Davis seek solutions through early detection methods, improved treatments, collaborative research across medical fields, and future vaccine development.
