An increase in seasonal agricultural work and the end of the school year in the San Joaquin Valley are expected to mean more people spending more time working and playing outside – and potentially increase the risk of Valley Fever, a fungal disease that can create respiratory problems in people who inhale its spores.
It’s also a disease for which there is no vaccine to help protect people from its effects.
Through the first three months of 2026, more than 1,200 confirmed or suspected cases of Valley Fever, also known as coccidioidomycosis, have been reported across Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus and Tulare counties. Cases in the San Joaquin Valley represent more than half of all cases reported in California in the first quarter of the year.
The Coccidioides fungus grows in the soil in the San Joaquin Valley and other parts of the state and southwestern U.S., and its microscopic spores that cause Valley Fever can be stirred up and become airborne when the soil is disturbed by digging, agricultural work or high winds. Those spores can be inhaled and settle in the lungs of both people and animals.
From 2001 through 2024 – the latest full year for which case data is available – almost 74,000 Valley Fever cases were identified in the San Joaquin Valley, according to the California Department of Public Health. That’s more than 62% of all cases statewide. And for that entire span, Kern County has accounted for more than 46,000 cases, making it the hot spot for Valley Fever in the region.
The 2026 caseload through the first three months of the year, however, is lower than the record pace of 2024 both in the Valley and statewide.
A mortality database maintained by the U.S. Centers for Disease Control and Prevention reported that coccidioidomycosis was associated with the deaths of 284 people in the San Joaquin Valley since 2018:
- Fresno County: 64 deaths.
- Kern County: 103 deaths.
- Kings County: 10 deaths.
- Madera County: 10 deaths.
- Merced County: 10 deaths.
- San Joaquin County: 27 deaths.
- Stanislaus County: 19 deaths.
- Tulare County: 41 deaths.
The official figures represent a Valleywide annual average of about 4,750 cases, including an average of 31 deaths each year since 2018.
Nationwide, the number of Valley Fever cases averages about 20,000, including about 200 deaths for which coccidioidomycosis is listed as a primary or contributing cause on a person’s official death certificate.
Cases likely underreported
But the actual numbers of cases and deaths are likely much higher than what’s in the official statistics. “Valley Fever is underestimated due to misdiagnosis, underdiagnosis, and lack of care seeking,” the CDC reported. Because of its relative rarity, its symptoms can be mistaken for other respiratory problems including pneumonia.
A 2025 article published by the Journal of the American Medical Association indicated that only 28 states plus Washington D.C. require doctors to report Valley Fever cases to state health officials, and that official totals “likely represent only a fraction of the true national burden of coccidioidomycosis.”
The CDC and the JAMA researchers estimate that the “true burden” of Valley Fever is likely 10 to 18 times more cases than reported – somewhere between 206,000 and 360,000 cases per year across the U.S. – while deaths may range from between 700 and 1,100 per year, or about five to six times more than reported.
If those estimates hold, that would suggest the annual average number of coccidioidomycosis cases in the San Joaquin Valley over the past decade is somewhere between 47,000 and 85,000, rather than the average of 4,750 since 2018. The underreporting and underdiagnosis could also place the number of deaths from the fungus in the Valley at between 157 and 190 per year since 2018.
“Detection of coccidioidomycosis is complicated by several factors, including barriers to health care access, people who do not seek care, underdiagnosis, underreporting,” as well as residence outside of regions where Valley Fever is known to be endemic,” the JAMA article states. “People who experience mild symptoms may never seek care, making it impossible to identify them.”
Additionally, the researchers noted, Valley Fever symptoms “may be indistinguishable from bacterial or viral community-acquired pneumonia.”
What does Valley Fever do?
Some people who have Valley Fever may never realize it because they don’t experience any symptoms and their immune system is enough to battle the infection.
But others aren’t as fortunate. Valley Fever symptoms can be mistaken for other respiratory diseases including COVID-19 and influenza.
“Most people who do get sick with Valley Fever have respiratory symptoms or pneumonia because the Valley Fever fungus usually infects the lungs,” the California Department of Public Health advises, adding that symptoms may begin to develop one to three weeks after the fungus spores are inhaled.
Symptoms can include fatigue or exhaustion, breathing difficulty, night sweats, muscle or joint pain, fever, chest pain, weight loss or a skin rash, particularly on the front of the legs. The symptoms can last for a few weeks to a few months.
“Symptoms can also become more severe and last much longer if the Valley Fever infection spreads to other parts of the body,” the CDPH reports. In rare cases, the fungus can infect the brain and cause meningitis, which can require lifelong treatment and, in extreme cases, can be fatal.
Brynn Carrigan, the director of public health in Kern County at the southern end of the San Joaquin Valley, was one of those rare Valley Fever meningitis cases.
“In May of 2024, I was diagnosed with the rarest and most severe form of Valley Fever called cocci meningitis, which is a Valley Fever infection in the brain and in the spine,” Carrigan said in a “Faces of Valley Fever” video produced by the county. “I had been sick for about a month with extremely painful, debilitating headaches.”
Carrigan said it took multiple visits to doctors over the course of the month before she was correctly diagnosed and treatment began.
Who’s at risk for Valley Fever?
Anyone who lives or works in the San Joaquin Valley or other areas with high rates of Valley Fever are at risk for the disease, especially if they work or do other activities that include contact with dirt or dust. Agricultural work, digging, gardening, landscaping, construction, firefighting, excavation, and other outdoor work where dirt and soil are stirred up are among activities that present added risk.
In addition, public health data shows that nearly half of reported Valley Fever cases in the state from 2001 through 2024 were among people of Hispanic or Latino origin. Other risk factors include being age 60 or older; pregnancy; diabetes; and health conditions that weaken the immune system, such as cancer, HIV, autoimmune illnesses, undergoing treatment with chemotherapy or steroids, or organ transplant.
Valley Fever isn’t contagious, however, so it cannot be spread from one person to another.
Pets and livestock can also get Valley Fever if they inhale the fungal spores into their lungs. And like humans, it can cause breathing problems such as a dry cough in dogs, or a skin infection in cats.
But it cannot be passed from an animal to people or from people to animals.
Limiting exposure to Valley Fever
The Fresno County Department of Public Health offers guidelines for ways to prevent or limit exposure to Coccidioides spores.
“It is difficult to avoid contact with the fungus spores, but people who live in endemic regions, such as areas in the western region of Fresno County, should avoid dusty areas and outside activity on windy days, if possible,” the agency warns.
The guidelines advise to:
- Stay indoors and close windows and doors during times of increased dusty winds.
- Wear a mask when doing activities that involve exposure to dust including yard work, gardening and digging in dry soil. Respiratory protection such as masks can reduce exposure by 90%.
- For outdoor workers, wear respiratory protection (with filters rated N95, N99, N100, P100 or HEPA) if it is necessary to be in or near a dusty area, such as a construction zone.
- Clean skin wounds well with soap and water, especially if they have been exposed to soil or dust.
- Wet the dirt before digging.
Tim Sheehan is the Health Care Reporting Fellow at the nonprofit Central Valley Journalism Collaborative. The fellowship is supported by a grant from the Fresno State Institute for Media and Public Trust. Contact Sheehan at tim@cvlocaljournalism.org.
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