Rising Valley Fever Cases in California: Prevention and Risk Factors

California is experiencing a concerning increase in valley fever cases as the state heads into a summer marked by longer, drier seasons. Public health officials warn that the ongoing dry conditions promote the growth and airborne dispersal of the fungus coccidioides, which causes valley fever, or coccidioidomycosis. Since the beginning of the year, over 4,000 cases have been reported statewide from January to April, representing a significant rise compared to previous years. Last year, California recorded a peak of 12,605 cases, while in 2023, the total surpassed 9,000.

Valley fever is a lung infection resulting from inhaling spores of coccidioides that reside in arid, disturbed soils in regions including the southwestern United States, parts of Mexico, Central, and South America. The spores are released into the air when the soil is disturbed by activities like wind, construction, or outdoor recreation.

The disease often manifests with symptoms such as cough, fever, chest pain, fatigue, and rash, which mimic other respiratory illnesses, making accurate diagnosis challenging. Symptoms typically develop within one to three weeks after exposure and can persist for several weeks or more. While many individuals experience mild symptoms requiring no treatment, others may develop severe complications, including pneumonia-like conditions, rashes, or even dissemination of the infection beyond the lungs.

Public health authorities note that the timing of valley fever cases is shifting, with transmission starting earlier in the year and lasting longer—an observation linked to climate change. Experts indicate that warmer, drier seasons and increased rainfall promote the conditions necessary for the fungus to thrive.

Certain groups are at heightened risk for developing severe disease. These include older adults over 60, pregnant women, children under five, and individuals with weakened immune systems such as those with diabetes, cancer, HIV, autoimmune disorders, or undergoing immunosuppressive treatments. Racial and ethnic minorities—including Black, Latino, Native American, and Filipino populations—are also more susceptible, although reasons for this disparity remain unclear.

Preventive measures are crucial, especially for those living in or visiting high-risk areas. Recommendations include staying on well-maintained trails during outdoor activities, wearing N95 masks in dusty conditions, avoiding outdoor activity during windy days, ensuring wounds are properly cleaned, and keeping indoor environments sealed during windy, dusty weather. When gardening or excavating soil, wetting the area beforehand can help reduce airborne spores.

Public health officials emphasize that outdoor workers such as construction crews, farmers, and archaeologists are particularly vulnerable due to their exposure to dusty environments. Wearing protective gear and adhering to safety protocols can significantly reduce risk.

If symptoms develop—particularly in individuals in or traveling through endemic regions—prompt consultation with healthcare providers is essential. Diagnosis often involves blood tests, and treatment usually involves antifungal medications, especially in severe cases. As climate patterns continue to evolve, vigilance and preventative strategies remain key to mitigating valley fever’s impact in California.

Source: https://medicalxpress.com/news/2025-05-valley-fever-cases-spike-california.html