The state reported 3123 cases, a significant jump from 2024's 1011 cases in the same period, with experts citing environmental factors.
In the first quarter of 2025, California reported 3,123 cases of Valley Fever (Coccidioidomycosis), nearly double the 10-year average for this period. This is the highest number reported for Q1 on record, surpassing the previous record of 3,011 cases in 2024. Following a record-breaking year in 2024 with 12,637 cases statewide, experts warn California may be on track to exceed last year’s total. Updated reports are still being anticipated. 1
Monterey County, CA, has seen a particularly sharp increase. In the first quarter of 2023, only 22 cases were reported. By the same period in 2025, the number had surged to 217. This increase is part of a larger trend of rising cases across the state, with some areas of the Central Valley seeing a 200% increase in cases over the past year.1
Valley Fever primarily affects the respiratory system, often presenting with flu-like symptoms. However, severe cases can lead to more serious conditions, including pneumonia that requires ventilator support. “We’re concerned that not only are there more cases, but there’s more severe disease,” said George Thompson, MD, professor of infectious diseases at UC Davis Medical Center in our January 2025 interview.2
In approximately 1% of cases, Valley Fever can spread from the lungs to other organs, including the brain, bones, and skin, potentially leading to meningitis. The rising number of cases and severity of the disease has resulted in increased admissions to intensive care units (ICUs). “We haven’t typically had this many patients with Valley Fever in the ICU at one time,” Thompson added.2
Several environmental factors are contributing to the rise in Valley Fever cases. The disease is caused by inhaling spores from the Coccidioides fungus, which thrives in dry, dusty regions. Experts point to the state’s fluctuating climate as a key factor. Wet conditions promote the growth of fungal spores, which are then released into the air when disturbed by human activities or natural events, such as wildfires.2
Thompson noted that, “In the soil, Coccidioides exists as a mold form. And during periods of heavy precipitation, when we get a good amount of rainfall, we think it grows into a higher quantity within the soil. And then during drought conditions, every other cell dies and spores are formed.” These spores can then be inhaled, causing infection.2
Wildfires, which have increased in California due to long droughts, may also contribute to the spread of Valley Fever. “Fire can create its own weather. It kind of updrafts air, and we’re concerned that those large updrafts might throw Valley Fever into the air and really facilitate spread into the surrounding region,” Thompson said.2
Emerging research also points to previously unrecognized environmental risk areas. In a recent study, we interviewed Jane Sykes, BVSc (Hons), PhD, MPH, MBA, from school of veterinary medicine, UC Davis School of Veterinary Medicine, and she analyzed over 830,000 canine serologic tests from across the US, finding that Coccidioides is likely present in far more counties than previously detected by human surveillance alone. The number of US counties with seropositive dogs increased more than five-fold over the past decade, from 76 counties in 2012 to 390 counties in 2022.3
California reported 3,123 Valley Fever cases in Q1 2025, the highest number for this period since tracking began.
Environmental conditions, including rainfall, drought, and wildfires, continue to drive increases in fungal spore exposure.
Canine testing data suggest wider distribution of Valley Fever than current human surveillance reflects, prompting calls for integrated monitoring.
“The dog serologic data analysis showed that the incidence in dogs closely follows that in humans, at least in California and Arizona,” Sykes said. This suggests that canine seropositivity could serve as a proxy for human exposure in areas where testing and reporting are limited. “We are currently performing additional studies with the data to extrapolate where unrecognized disease might be occurring in humans—both in locations where reporting is required and in other parts of the country.”3
Sykes emphasized that integrating veterinary and human data through a One Health approach could improve early detection and inform occupational health strategies in emerging risk areas. “There may be implications for occupational exposure reduction, such as education of construction workers, military personnel, agricultural workers, or wildfire fighters regarding the need for PPE and dust avoidance,” she noted.3
Certain occupations and regions are at higher risk for Valley Fever. People working in construction, firefighting, and archaeology are particularly vulnerable due to their frequent exposure to disturbed soil. Additionally, residents of dry, arid areas, such as those in Central and Southern California, are at increased risk.4
Valley Fever is typically treated with antifungal medications such as fluconazole and itraconazole, but some patients do not respond to these treatments, complicating management.4 “Some of those patients don’t respond to any agent, and that’s really a challenge for how we improve these patients,” Thompson explained. In these cases, immunotherapy may be used to enhance the body’s immune response.2
Prevention Efforts and Advice
Health officials have issued several recommendations to reduce the risk of infection, particularly in dust-prone areas. Monterey County has advised local medical providers to be vigilant and issued guidance urging residents to avoid dust exposure. At events like the Lightning in a Bottle festival, organizers are taking steps to reduce dust, including watering the grounds and using artificial turf.1
To prevent infection, health experts recommend limiting exposure to dust, especially during dry conditions or after rainfall. Individuals who live in or visit areas with a high risk of Valley Fever should be alert to flu-like symptoms, including cough, fever, chest pain, and fatigue. Early medical consultation is essential if symptoms worsen or do not improve.4
