Coccidioidomycosis, also known as Valley fever, is an infection caused by breathing in the spores of the fungus Coccidioides found in the soil in the southwestern United States and California, northern Mexico and parts of Central and South America. It is a common cause of pneumonia in Arizona and California but can also be found in parts of Utah, Nevada, Texas and New Mexico. People who either live in or travel through these areas are at risk for infection.

Key Facts

  • Coccidioidomycosis is not contagious, meaning it cannot be passed from person to person.
  • Most people who get coccidioidomycosis have minimal symptoms and do not require treatment.
  • Symptoms appear between one to three weeks after exposure and last a few weeks to a few months.
  • Only about five to ten percent of people who get Valley fever will develop serious or long-term lung problems. Less than one percent will have the disease spread to other parts of the body.
  • Currently, there is no vaccine to prevent Valley fever.

How Coccidioidomycosis Affects Your Body

Once inhaled, the Coccidioides fungus multiplies and spreads, leading to the progression (worsening) of the disease. The time from exposure to the development of symptoms may take several weeks. Because the fungus is inhaled, the disease typically affects the lung. In a small number of people, it may spread outside of the lung and affect other parts of the body. This serious complication is called “disseminated coccidioidomycosis.” Another serious complication that could occur is pneumonia.

Who Is at Risk for Coccidioidomycosis?

Not everyone who is infected by Valley fever will have symptoms. If you are concerned you may be at risk, you should talk to your doctor.

People living in or traveling to regions where the Coccidioides fungus occurs are at risk of infection. Exposure to dust storms or areas where contaminated soil is being disturbed, such as construction sites or farms, may increase your risk. People who have compromised immune systems are at increased risk of developing severe or disseminated disease. These include:

  • People with HIV infection
  • People taking immune-suppressing medication therapy for autoimmune or rheumatologic diseases
  • Organ transplant recipients
  • People with diabetes
  • Pregnant women

When to See Your Doctor

If you live in or have traveled to an area where Valley fever occurs and develop these symptoms, you should consult with your healthcare provider.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: November 17, 2022

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