California Valley Fever Cases on Track for Record High

California surpassed 5,500 provisional cases of valley fever in the first six months of 2025, putting the state on track to hit record levels, according to a new snapshot of data from the state’s Department of Public Health.

Last year, California saw 12,500 valley fever cases, the highest year on record in the state, and a major jump from the 7,000–9,000 cases reported annually from 2017 through 2023.

Valley fever — a fungal disease spread by airborne spores — is marked by symptoms similar to COVID-19, like coughs and fevers. The disease can also cause serious lung infections, like pneumonia.

Most infections are mild. But Dr. Stuart Cohen, an infectious disease specialist at UC Davis, said he’s seeing more severe cases, even in otherwise healthy patients.

“We are seeing higher numbers, and it seems like we’re seeing sicker patients too,” Cohen said.

Research has linked the increase in valley fever to an increase in dust storms and droughts due to climate change.

State health officials note that rates of valley fever continue to be highest in the southern San Joaquin Valley, but are also increasing in other areas, including the northern Central Valley and the Central Coast.

As of July 31, provisional data from the state’s health department showed Alameda County reported 72 valley fever cases, while Contra Costa County had 105 cases.

Cohen said a wet winter two years ago may have played a role in the increase.

“It’s a mold. And so wet winters help the mold grow,” Cohen said. “Dry summers, particularly dry summers with wind, allow the organism to be blown around and then inhaled by people, which ultimately causes infections.

Researchers at UC Berkeley published a study this year showing that longer, drier summers in California can extend the disease’s transmission. The researchers call for targeted interventions, such as raising awareness among at-risk populations and improving diagnostic testing during peak periods.

Research from the National Institutes of Health found that dust storms, exacerbated by climate change, also contribute to valley fever’s spread, transporting fungal spores over long distances and exposing larger populations to the risk of infection. Construction in high-risk areas may also contribute to an increase in reports of valley fever.

According to the Centers for Disease Control and Prevention, valley fever is underdiagnosed, and thousands of cases are not reported.

“We want to remind Californians, travelers to California, and their healthcare providers to watch for signs and symptoms of valley fever to help detect it early,” CDPH Director and state public health officer Dr. Erica Pan said in a statement.

The Department of Public Health is reminding residents — especially those who have been outdoors in dusty air in the Central Valley or Central Coast regions — to inquire with healthcare providers if they experience symptoms like cough, fever or trouble breathing for seven days or more.

Residents are also advised to keep windows and doors closed when it is windy outside and the air is dusty, and to keep windows closed when driving through dusty areas.

KQED’s Madi Bolaños contributed to this report.