Valley Fever (Coccidioidomycosis)


Valley Fever (Coccidioidomycosis) is an illness caused by the soil fungus Coccidioides that lives and grows in the Western United States. There were approximately 20,000 infections (reported) diagnosed in the US in 2019, with the greatest number diagnosed in California and Arizona. Infection occurs when spores of Coccidioides in soil or dust are disturbed, carried through the air, and inhaled. In extremely rare cases, spores can also infect the skin through abrasions and open cuts or sores. The disease cannot be transmitted from person to person. Many people who are exposed to the fungus Coccidioides never show symptoms.

Symptoms of Valley Fever may appear between one and three weeks (7 to 21 days) after exposure and can be mild to severe, lasting from weeks to months. The most common symptoms are cough, fever, shortness of breath, headache, fatigue, and body aches among others (Figure 1.). Although most symptoms resolve on their own, people who have underlying health conditions or weakened immune systems can develop chronic lung disease. Chronic Valley Fever may develop many years after initial infection and is long lasting; roughly 5-10% of individuals who have Valley Fever get this long-term disease. (Figure 1.)

In rare cases (0.5-1%), people sick with Valley Fever can develop disseminated disease and the infection spreads to other areas of the body including the central nervous system, bones, joints, and skin (Figure 1.). Disseminated disease is more likely to occur when a large amount of contaminated dust is inhaled. Those most at risk include:

Valley Fever Outbreaks in Workers

The geographic risk of exposure to Coccidioides is currently limited to dry regions of the western United States. Any work activity that disturbs dust in a region where Coccidioides grows puts workers at risk for Valley Fever. Jobs with increased risk of exposure include agricultural workers, construction workers, archeologists, geologists, and wildland firefighters.

  • In the summer of 2001, 10 workers at an archaeological dig in Dinosaur National Monument, Utah, became ill with Valley Fever and sought medical care within two weeks of the excavation.
  • In January 2012, 10 workers on an outdoor film set in Ventura County, CA experienced symptoms of Valley Fever, five of which were confirmed cases and tested positive, and five of which were probable cases. Soil disruption from grading, digging, and filling a pit occurred shortly before filming.
  • In 2016, solar farm construction workers in Monterey County, California were diagnosed with Valley Fever at more than 62 times the rate of diagnosis for the general population in Monterey County.
  • A 2020 study of Valley Fever in Hispanic farm workers in Kern County, California showed that dust exposure and work with root and bulb crops were common factors among those who became ill.
  • In July 2021, seven wildland firefighters were reported to have Valley Fever after working on wildfires in the Tehachapi Mountains. All reported digging trenches and moving soil without respiratory protection.