What is Valley fever?

Valley fever, also called coccidioidomycosis, is an infection in the lungs caused by a Coccidioides fungus that is usually found in the southwest United States, Central and South America, and Washington state. The condition is usually mild and gets better on its own, but some people with moderate to severe infections may need antifungal drugs to cure the disease. Valley fever is also known as San Joaquin Valley Fever or desert rheumatism.

Who is most at risk for getting Valley fever?

Anyone who breathes in the fungus can become infected, but Valley fever is most common in adults over age 60. People who have recently traveled or moved to an area where the fungus lives may be more likely to get the infection. Valley fever is also more likely to occur in certain high-risk individuals, including people who:

  • Have weakened immune systems, which can be caused by certain medications or diseases like HIV/AIDS
  • Are pregnant
  • Live with diabetes
  • Belong to certain ethnic groups, including African-Americans and Filipinos
  • Work at jobs that expose them to soil dust

What causes Valley fever?

There are two forms of Coccidioides immitis. One form (the mycelial form) grows beneath the hot desert sands and soils. Disturbing the sand causes the tiny branches (hyphae) of the fungus to break apart and release individual spores (arthoconidia). These microscopic spores are then inhaled and settle into the branching system of the lungs. The spores then transform into thick walled spherules, within which, on maturity, thousands of endospores develop (the yeast phase). It is the yeast forms in tissue that allow the diagnosis of Coccidioides immitis to be made.

Although the spores are very infectious, Valley fever is not contagious — it cannot spread from person to person.

What are the symptoms of Valley fever?

Because Valley fever develops in the lungs, its symptoms are like those of the flu (influenza).

Symptoms of Valley fever may include:

Often, Valley fever infections don’t cause any symptoms. Mild flu-like symptoms may disappear on their own after a few weeks or months. With a severe infection, symptoms may last longer.

Last reviewed by a Cleveland Clinic medical professional on 03/19/2018.


  • Centers for Disease Control and Prevention. Valley Fever. Accessed 4/11/18.
  • American Association for Clinical Chemistry. Fungal Tests. Accessed 4/11/18.
  • Garcia SCG, Alanis JCS, Flores JCS, et al. Coccidioidomycosis and the skin: a comprehensive review. An Bras Dermatol. 2015 Sep-Oct;90(5):610-619.
  • Coccidioidomycosis. Merck Manual Consumer Version. Accessed 4/11/18.

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