Valley Fever (Coccidioidomycosis)


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

Symptoms and Causes

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.

Diagnosis and Tests

How is Valley fever diagnosed?

Most infection with C. immitis does not cause symptoms. The lungs are the most common organ infected. It is often abnormal chest X-rays or a CT scan of the chest (a type of X-ray that makes cross-sectional images of your body), that may raise the possibility of Valley fever.

A blood test for coccidioidal serology may also help to diagnose Valley fever.

Management and Treatment

How is Valley fever treated?

In many cases of Valley fever, no treatment is necessary because symptoms disappear on their own. People with more serious infections may need antifungal medications to cure the infection. Doctors usually prescribe antifungal medications for a period of 3 to 6 months. In some severe cases, people require hospitalization or long-term antifungal treatment.

What complications are associated with Valley fever?

Only a small number of people experience a severe Valley fever infection, which can cause serious and long-term lung problems. It is also possible for the infection to spread to other parts of the body. These complications are not common.


Can Valley fever be prevented?

Unfortunately, it’s hard to avoid breathing in Coccidioides fungal spores if you live in an area where they are common. While you may not be able to prevent Valley fever completely, you can take steps to reduce your risk for developing it.

  • Avoid areas where you will be exposed to dirt or dust, if possible. If you must be in these areas, use an N95 respirator mask to help filter fungal spores out of the air you breathe.
  • Close your windows and stay inside during dust storms.
  • Avoid activities like gardening, digging, or other yard work that can expose you to fungal spores.
  • Use air filters indoors.
  • If you have a cut or scrape on your skin, be sure to clean the injury well with soap and water. This can help you avoid possible skin infection.

Outlook / Prognosis

What is the prognosis (outlook) for people with Valley fever?

In most cases, people with Valley fever infections make full recoveries. However, a small number of people develop persistent lung infections that may take several years to resolve. In certain severe cases, Valley fever can affect the nervous system and lead to chronic complications.

Living With

When should I call my doctor?

If you live in an area that’s known to harbor Coccidioides fungal spores, and you’ve had flu-like symptoms for more than one week, contact your doctor. He or she can order the blood test to determine if you have the infection.

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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