With Valley fever cases climbing in California, physicians have struggled to treat the increasing number of patients grappling with the deadliest version of the disease. When Valley fever, or coccidioidomycosis, spreads from the lungs, it can cause infected joints, scarred lungs and even deadly meningitis.
Now, researchers appear to have found a major breakthrough studying an experimental drug that helped the sickest patients, who otherwise had run out of treatment options
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The study’s results, published Monday in the Annals of Internal Medicine, looked at whether an experimental antifungal medication called olorofim could help relieve symptoms of people with disseminated Valley fever, meaning their disease has spread beyond their lungs. The team found a significant number, over 70%, of patients with the stubborn and potentially deadly form of disease were helped after taking the new drug.
Dr. Fariba Donovan, a researcher at the University of Arizona Valley Fever Center for Excellence and lead author of the study, said some of her patients regained the ability to walk and drive after receiving the medication
“I feel like this is going to be a big game changer,” she said.
Valley fever is an insidious disease caused by a fungus hidden in the dried soil of California, Arizona and other Western states. Microscopic spores of the Coccidioides can become airborne as hot and dry conditions turn the soil to dust. When people breathe in these spores, the spores get lodged in the lungs and, in some cases, start to replicate.
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Most people, about 60%, exposed to the spores won’t have any symptoms. Around 30% may develop flu-like symptoms that last weeks to months, and 5% to 10% of patients will develop serious and long-term lung issues. About 1% of patients will develop disseminated Valley fever, where the disease spreads from the lungs to other key areas, including joints, skin or the brain.
In California, cases of coccidioidomycosis have risen nearly tenfold in the past two decades, going from 1,492 cases in 2001 to a high of 12,444 in 2024. Cases dipped slightly in 2025 to 10,714, according to preliminary information from the California Department of Public Health. So far, California is on track for more than 10,000 cases this year
The first treatment for people with Valley fever is with a class of antifungal treatments called azoles. These first-line treatments can be effective at controlling the fungus but can also have harmful side effects for some patients or become less effective depending on the severity of a person’s illness
In the latest study, physicians from multiple institutions, including the University of Arizona Valley Fever Center for Excellence, studied 41 patients diagnosed with disseminated Valley fever. The patients were either no longer responding to traditional medications or had too many side effects to keep taking the drugs.
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Between May 2019 and August 2022, the individuals enrolled in the study were given either olorofim or both olorofim and the traditional treatment for Valley fever. Many of the patients had severe symptoms, including 30 with central nervous system disease.
Olorofim is an antifungal medication that is a type of enzyme, not yet approved by the U.S. Food and Drug Administration for treatment. It works by blocking a key RNA and DNA synthesis, which causes cell death
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The treatment also didn’t eradicate the fungus from the patients, meaning they needed to stay on the medication to keep symptoms at bay
But despite the limitations, Donovan said the medication appeared to be beneficial for patients
“We enrolled people who absolutely had no alternative option later in their disease,” she said.
She said of the 14 patients enrolled at her site, nine are still on the medication thanks to the FDA compassionate use designation. Some of the patients did report side effects, with one patient dropping from the study. Donovan said they were able to modify medication for most other patients to address side effects, including elevated liver enzymes
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Donovan said she is working on a new study to see if the medication, when given earlier, can eradicate the disease
Dr. Shangxin Yang, an associate clinical professor of pathology and laboratory medicine at UCLA, called the study results “phenomenal” and told SFGATE a new drug “is exactly what we need at this point.”
Yang said when he started his career 15 years ago, Valley fever in California was still relatively uncommon, and he saw only about one Valley fever case a month. Now, he said, he often sees at least one case a day
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“The cases are still trending up,” Yang, who was not involved in the study, told SFGATE. “There’s no stop.”
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Yang also highlighted that 39 of the 41 patients in the study were not immunocompromised when they became ill.
“This disease does not spare the healthy population,” he said
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