Recent news reports are bringing awareness to Valley fever (or pulmonary coccidioidomycosis), an infection caused by the Coccidioides fungus. The fungus is typically found in California, Arizona, Utah, Texas, New Mexico, and Nevada soil. Experts say climate shifts may lead to its spreading northward, however.
The CDC says there were 20,003 reported cases of Valley fever in 2019, but numbers are likely even higher.
Symptoms include fever, night sweats, body aches, fatigue, cough, difficulty breathing, and rash. Valley fever has led to long-term complications and even meningitis.
A dangerous and deadly fungus that causes Valley fever is spreading across the country slowly as the climate warms. Here's what you need to know.
In 2018, an 18-year-old University of Arizona student, Devin Buckley, found himself unable to walk without getting winded. Buckley also experienced “rapid weight loss, stomach problems, and extreme fatigue that seemed to come out of nowhere,” NBC reports. Eventually, he was placed in intensive care, struggling to breathe independently.
At first, healthcare practitioners could find no answer, opting to test Buckley for cancer. NBC says a family friend then suggested that he be tested for Valley fever. Buckley tested positive.
But what is Valley fever?
Shirin Mazumder, MD, an infectious diseases physician at Methodist Le Bonheur Healthcare in Memphis, Tennessee, says Valley fever is caused by the Coccidioides fungus (both Coccidioides immitis or Coccidioides posadasii), which has historically been found in the soil of certain United States regions, like California, Arizona, Utah, Texas, New Mexico, and Nevada. However, experts tell UCLA Health that the fungus appears to be spreading Northward (it’s been seen in Washington) as climate shifts occur, with predictions that it will be seen across half the country in the coming decades.
“The fungal spores can become airborne when contaminated soil and dust are disturbed by animals, weather, or human activity,” Dr. Mazumder says. And when people breathe in the spores, transmission can occur. “People can become infected if they inhale spores from a wound contaminated with Coccidioides, have contact with objects that have been contaminated with Coccidioides, or from organ transplantation if the donor was infected,” Dr. Mazumder says.
According to the Centers for Disease Control and Prevention (CDC), there were 20,003 reported cases of Valley fever in the United States in 2019, most frequently in Arizona or California.
The CDC says that that number is likely even higher, as “Tens of thousands more illnesses likely occur and may be misdiagnosed because many patients are not tested for Valley fever,” they say. “In highly endemic areas such as the Phoenix and Tucson metropolitan areas of Arizona, Valley fever causes an estimated 15% to nearly 30% of community-acquired pneumonia, but low testing rates suggest that Valley fever is probably under-recognized.” It typically affects patients over the age of 60. 
Diagnosing and treating Valley fever
Dr. Mazumder says that Valley fever specifically refers to lung involvement of Coccidioides but that the infection can also involve other organs. “When the fungus spreads beyond the lungs, it can involve the bone and joints, skin, genital tract, and central nervous system,” she says.
This is what’s referred to as ‘disseminated disease.’ Patients at higher risk of disseminated disease include pregnant women, the immunocompromised, and patients with diabetes, she adds.
Symptoms—which typically begin one to three weeks after exposure to the fungus—may include “fever, night sweats, body aches, fatigue, cough, difficulty breathing and rash….For [some patients], symptoms can last anywhere from weeks to months, all depending on the severity of the infection.” On the other hand, some people exposed to the fungus, she says, won’t become ill at all.
Scott Roberts, MD, assistant professor, associate medical director, and infection prevention professor at Yale School of Medicine, says that patients with high risk of severe disease—like the immunocompromised—or those with serious symptoms “may qualify for treatment with an antifungal medication called fluconazole.”
Dr. Mazumder also says severely ill patients can be treated with amphotericin, an antifungal medication given intravenously. Treatment can last anywhere from three to six months or even longer. Most people, she says, will recover. Others, however, can develop long-term lung issues, like meningitis due to Coccidioides.
“This infection can be fatal, and usually patients are maintained on lifelong antifungal medication with central nervous system infection,” Dr. Mazumder notes.
In Buckley’s case, the disease disseminated from his lungs to his spine and legs, requiring him to use a ventilator on three separate occasions, sometimes for weeks at a time.
“Buckley has relearned how to walk, feed himself, and accomplish basic daily tasks, but he’s still not out of the woods. His life is radically different from what it was like before he got sick, filled with doctor’s appointments, surgeries, and hospital stays,” NBC reports.
Other patients have died. A 2023 case report published in the Journal of Medical Cases found a 46-year-old with a recent diagnosis of pulmonary coccidioidomycosis. The patient initially experienced acute respiratory failure and was found to have coccidioidomycosis meningitis.
“This case highlights that despite early and adequate treatment of a known pulmonary coccidioidomycosis infection, dissemination of the disease can still ensue and should be considered in cases of acute encephalopathy,” the authors write. The patient died after 24 days.
Diagnosis and prevention
To make matters less confusing, a simple blood test—which looks for the presence of Coccidioides antibodies or antigens—can diagnose Valley fever. X-rays or CT scans of the lungs may also help fill in the blanks.
Dr. Roberts says the best way to prevent infection is to avoid inhaling the spores—usually by avoiding dust storms or construction sites where the soil is kicked up. “Use a respirator mask (such as an N95) when you do have to inhale dust and filter the air indoors if possible,” he stresses.