A soil-dwelling fungus long tied to the American Southwest is gaining ground in cool, coastal, and temperate regions, turning new communities into hotspots. Valley fever, the illness caused by Coccidioides spores, is accelerating amid climate volatility, and public health officials are urging vigilance ahead of seasonal surges. California reported nearly 12,500 cases in 2024, a record that far outpaces the roughly 1,000 cases logged less than 25 years ago. The trend is not confined to traditional desert counties; cooler coastal areas are now seeing sharp increases that reflect a broader shift in where the fungus can thrive.
What valley fever is and how it spreads
Valley fever begins when people inhale microscopic spores that live in dry soils. Disturbed ground and windy days can loft spores into the air, which means everyday activities like gardening, outdoor recreation, and nearby construction can be enough to cause exposure. Symptoms usually appear one to three weeks after breathing in spores and often mimic pneumonia or the flu. Many people experience cough, fever, fatigue, and chest pain that can last for weeks or longer.
Most cases are mild to moderate respiratory illness, yet the disease can become serious. About 5% to 10% of infections lead to prolonged lung complications, and roughly 1% disseminate to the brain, bones, or other organs. People with weakened immune systems, those who are pregnant, and individuals with diabetes face higher risk for severe disease. Certain racial and ethnic groups, notably Black and Filipino individuals, are also more likely to develop complicated infections. Antifungal medications can reduce the risk of severe outcomes when started promptly. Natural infection often leads to lasting immunity, and there is currently no vaccine.
Climate and environmental drivers behind the surge
The driver behind today’s expansion is a changing climate coupled with land use patterns that kick up dust. Periods of heavy rain followed by drought appear to boost spore production, then dry conditions help spores become airborne. Rising temperatures and longer dry spells are expanding suitable habitats for the fungus beyond historic deserts. Dustier conditions from construction, agriculture, and wildfire recovery increase exposure risk for workers and nearby residents alike.
These pressures are no longer limited to classic high-exposure settings. Agricultural and construction workers, as well as incarcerated populations, remain vulnerable. Yet the risk now reaches people in fast-growing suburbs and those enjoying outdoor leisure activities, from trail running to golf. The result is a wider pool of potential exposure in places that once felt safely outside the endemic map.
California’s upward trajectory is particularly stark. The 2024 total of nearly 12,500 reported cases caps a steep climb from the early 2000s and underscores how the disease has moved beyond the San Joaquin Valley. Coastal and cooler counties are reporting sharp increases, challenging assumptions that the ocean air keeps valley fever at bay. Beyond the Southwest, documented infections have reached Oregon and Washington. Projections suggest the fungus could extend its range into Canada and the Midwest by the end of the century if warming trends continue.
Diagnosis delays and why they matter
Awareness has not kept up with the new reality, and that gap has consequences. Valley fever is frequently mistaken for bacterial pneumonia, influenza, or bronchitis, which can lead to multiple antibiotic prescriptions that do not help. Each delay raises the risk of complications, including spread beyond the lungs. Early testing and targeted antifungal therapy are critical for preventing severe outcomes. Health systems and nonprofits in affected counties now host regular information sessions to help people recognize symptoms and ask for testing when appropriate. Public health officials also stress that completely avoiding dust is unrealistic, so vigilance and a high index of clinical suspicion are essential.
Personal stories reveal how pervasive exposure can be. A healthcare worker in a high-incidence county reported that her dog likely contracted valley fever from backyard soil, a reminder that spores are part of the local environment. Patient educators in the region run monthly virtual sessions to guide families through diagnosis, treatment, and self-advocacy with their providers. In a separate case, a Central Coast resident without classic occupational risks developed persistent respiratory symptoms that were followed months later by neurological issues. After seizures and a diagnosis of hydrocephalus, spinal fluid testing confirmed disseminated disease. Ongoing management includes procedures to drain excess fluid, and the patient urges earlier awareness to prevent catastrophic outcomes for others.
