Creative Endeavors/Shutterstock

In the western United States, the fungus Coccidioides is responsible for valley fever, the acute form of coccidioidomycosis. While the Centers for Disease Control and Prevention (CDC) officially records about 20,000 cases each year, under‑reporting suggests that as many as 360,000 people may be infected annually. The disease is contracted when spores from dry soil are inhaled, leading to a lung infection that can cause shortness of breath, fever, chest pain, and fatigue.

Valley fever accounts for roughly 15–30% of community‑acquired pneumonia cases in Phoenix and Tucson. Though most infections are mild or asymptomatic—about 60% of cases show no symptoms—5–10% develop lasting complications. Individuals with weakened immune systems, diabetes, those on immunosuppressants, pregnant women, and Black and Filipino populations face the highest risk. In severe cases, the infection can progress to organ failure, and approximately 200 deaths are reported each year.

Climate Change Amplifies the Spread of Valley Fever

Dmitri Zelenevski/Getty Images

Since 2014, California’s recorded infections have quadrupled, while Arizona has seen a 73% rise over the past decade. Improved diagnostics partly explain this trend, but climate change is a major driver. Coccidioides can survive droughts by entering a dormant state; when rainfall follows a dry period, the fungus reactivates, releasing spores into the air. Warmer temperatures increase rainfall variability, intensifying both droughts and heavy precipitation events. Additionally, wildfires—more frequent and longer-lasting under climate change—scatter spores over large areas, accelerating regional expansion. Climate models predict that by 2100 the disease’s endemic zone could more than double.

How to Reduce Your Infection Risk

Emilie Saylor/Getty Images

Outdoor workers such as archeologists, firefighters, landscapers, and construction crews are especially exposed to dust storms and disturbed soil. While no vaccine exists, several precautionary measures can lower risk:

• Wear a mask: Use a N95 or higher respirator when working in high‑risk areas.
• Monitor weather: Avoid outdoor activities during dust storms or after heavy rains.
• Seal your home: Keep windows and doors tight to prevent spores from entering indoor spaces.

Pets can also contract the disease, particularly dogs that dig in soil. Most animal cases are mild, but severe symptoms can arise. Keep dogs on sidewalks and monitor for coughing, lethargy, or breathing difficulties. If your pet shows symptoms, consult a veterinarian promptly.

With climate change continuing to intensify, valley fever will likely become more common. Stay informed about local outbreaks, practice preventive measures, and seek medical attention if you experience shortness of breath or persistent cough.