LOS ANGELES — As the fungus that causes Valley fever expands across the western United States and cases skyrocket in California, researchers say they may have found a new drug that can help those suffering from the most advanced form of the disease.

And they're hoping that someday the anti-fungal drug known as Olorofim can be given to patients in earlier stages of the illness — before the fungal infection becomes too perilous.

"Olorofim actually kills the fungus," said Fariba Donovan, an associate professor at the University of Arizona's College of Medicine and a researcher with its Valley Fever Center for Excellence. Other drugs, she said, work by suppressing its growth.

Valley fever is caused by the fungus Coccidioides, which thrives in dry soil. People get it by breathing in the arid dust. While most who are exposed never develop symptoms, roughly 40% of people do. Most will have mild respiratory illness, which patients and doctors often mistake for influenza, Covid or other cold viruses. But roughly 10% experience serious lung problems, and 3-5% of those patients develop disseminated disease — which is rare but very serious and affects the brain and spine rather than the lungs.

If left untreated, those with severe disease often die.

Because it is often incorrectly diagnosed in its early flu-like stages, it can go unidentified and untreated for months. The biggest risk is for visitors to fungal-thriving places such as the San Joaquin Valley or Phoenix, who then return home to communities where valley fever is uncommon or nonexistent, such as the East Coast, Midwest or San Francisco.

"We encourage patients to ask their providers about Valley fever, and bring it up," if they are suffering from a cold that lingers or experiencing severe migraine-like headaches that don't seem to go away, said Donovan, who was lead author on a new study of the drug.

Patients who develop severe symptoms are typically treated with anti-fungal medications, such as fluconazole or itraconazole, which they must take for the rest of their lives. The drugs themselves can have severe side effects, such as hair loss and cracking, painful, dry skin.

In the study, published this week in the journal Annals of Internal Medicine , a multi-state team of researchers treated patients with severe cases of Valley fever with Olorofim, which was developed for immunocompromised patients vulnerable to fungal infections.

A phase III study of the medication in immunosuppressed patients infected with the fungus Aspergillus showed it worked as well as standard treatments, but with significantly fewer side effects. Phase III trials usually involve many people and are typically the final stage, if successful, before Food and Drug Administration approval.

For this trial, 41 patients were enrolled between May 2019 and August 2022. Nearly all — 95% — had been healthy before being exposed to Coccidioides. Two had suppressed immune systems before contracting the disease.

"That's really important," Donovan said. "It's a disease that can make previously healthy people really sick."

The infection had spread to the brain or spinal cord in 30 patients, which is extremely dangerous and hard to treat, and 13 were so ill they had what's called a ventriculoperitoneal shunt, a surgically implanted device in the head used to drain excess brain fluid caused by the infection or to deliver medication directly into the brain fluid.

The drug was deemed successful. By the 42nd day of treatment, more than three-quarters of the patients had improved or stabilized. By day 84, 73% were still seeing success.

George Thompson, professor of medicine at the UC Davis School of Medicine, said this was a "salvage" trial for patients who had failed current, standard forms of treatment.

"This was great, because we're always going to have patients who fail" the standard form of treatment, he said. "Hopefully, in the future, a head-to-head first-line trial can be done" to test Olorofim against other anti-fungals, as was done in the Aspergillus trial.

Thompson said it's still unclear whether patients treated with Olorofim will have to take it indefinitely, but he's hopeful the drug might be an option "to give people a final round of treatment so they can be off the drug."

The drug has not yet been approved by the FDA for treatment of Valley fever. However, patients such as those enrolled in this trial, doctors and others may contact the drug company with a request for compassionate use.

Thompson said he's seeing an increase in patients with the disease, and more presenting with severe symptoms. And although his research shows this change in severity is probably due to the overall increase in case numbers, he said the immunosuppressed population is growing, too.

Given the susceptibility of these patients to fungal diseases, he's hopeful more Olorofim-type drugs will make it to market.

Over the past 20 years, Valley fever cases in California have been on the rise. In 2024, there were 12,745 cases statewide, and 10,714 in 2025. In comparison, 2001 saw just 1,492 cases, and 2011 had only 5,234. So far this year, there have 5,102 cases have been reported to the state's public health department.

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