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A fungal infection caused by coccidioides immitis. Affected individuals usually have mild flu-like symptoms. However, pneumonia and systemic involvement with the formation of abscesses may develop as complications of the disease.

Coccidioidomycosis involving skin
Coccidioidomycosis involving skin

Other names

  • Valley fever
  • San Joaquin Valley fever or
  • Desert rheumatism


Valley fever is an infection caused by the fungus Coccidioides.

Scientific name

The scientific name for Valley fever is “coccidioidomycosis,” and it’s also sometimes called “San Joaquin Valley fever” or “desert rheumatism.” The term “Valley fever” usually refers to Coccidioides infection in the lungs, but the infection can spread to other parts of the body in severe cases (this is called “disseminated coccidioidomycosis”).

Coccidioidomycosis Spherule
Coccidioidomycosis Spherule


The fungus is known to live in the soil in the southwestern United States and parts of Mexico and Central and South America. The fungus was also recently found in south-central Washington. People can get Valley fever by breathing in the microscopic fungal spores from the air in these areas. Most people who breathe in the spores don’t get sick, but some people do. Usually, people who get sick with Valley fever will get better on their own within weeks to months, but some people will need antifungal medications. Certain groups of people are at higher risk for developing the severe forms of the infection, and these people typically need antifungal treatment. It’s difficult to prevent exposure to Coccidioides in areas where it’s common in the environment, but people who are at higher risk for severe Valley fever should try to avoid breathing in large amounts of dust if they’re in these areas.

Many people who are exposed to the fungus Coccidioides never have symptoms. Other people may have flu-like symptoms that go usually away on their own after weeks to months. If your symptoms last for more than a week, contact your healthcare provider.


Symptoms of Valley fever include:

In extremely rare cases, the fungal spores can enter the skin through a cut, wound, or splinter and cause a skin infection.2

Symptom onset

Symptoms of Valley fever may appear between 1 and 3 weeks after a person breathes in the fungal spores. The symptoms of Valley fever usually last for a few weeks to a few months.3, 4 However, some patients have symptoms that last longer than this, especially if the infection becomes severe.


Approximately 5 to 10% of people who get Valley fever will develop serious or long-term problems in their lungs.4 In an even smaller percent of people (about 1%), the infection spreads from the lungs to other parts of the body, such as the central nervous system (brain and spinal cord), skin, or bones and joints.

Coccidiodes lesion
Coccidiodes lesion

Risk factors

Anyone who lives in or travels to the southwestern United States (Arizona, California, Nevada, New Mexico, Texas, or Utah), or parts of Mexico or Central or South America can get Valley fever. Valley fever can affect people of any age, but it’s most common in adults aged 60 and older. Certain groups of people may be at higher risk for developing the severe forms of Valley fever, such as:

People who have weakened immune systems, for example, people who:

  • Have HIV/AIDS
  • Have had an organ transplant
  • Are taking medications such as corticosteroids or TNF-inhibitors
  • Pregnant women
  • People who have diabetes
  • People who are Black or Filipino

Not contagious

The fungus that causes Valley fever, Coccidioides, can’t spread from the lungs between people or between people and animals. However, in extremely rare instances, a wound infection with Coccidioides can spread Valley fever to someone else, 8 or the infection can be spread through an organ transplant with an infected organ. 9

Traveling to an endemic area

The risk of getting Valley fever is low when traveling to an area where Coccidioides lives in the environment, such as the southwestern United States, Mexico, or Central or South America. Your risk for infection could increase if you will be in a very dusty setting, but even then the risk is still low. If you have questions about your risk of getting Valley fever while traveling, talk to your healthcare provider. You can also consult CDC’s Travelers’ Health Yellow Book for more information.

It’s very difficult to avoid breathing in the fungus Coccidioides in areas where it’s common in the environment. People who live in these areas can try to avoid spending time in dusty places as much as possible. People who are at risk for severe Valley fever (such as people who have weakened immune systems, pregnant women, people who have diabetes, or people who are Black or Filipino) may be able to lower their chances of developing the infection by trying to avoid breathing in the fungal spores.

Coccidioidomycosis - PAS stain
Coccidioidomycosis - PAS stain

The following are some common-sense methods that may be helpful to avoid getting Valley fever. It’s important to know that although these steps are recommended, they haven’t been proven to prevent Valley fever.

Try to avoid areas with a lot of dust like construction or excavation sites. If you can’t avoid these areas, wear an N95 respirator (a type of face mask) while you’re there.

  • Stay inside during dust storms and close your windows.
  • Avoid activities that involve close contact to dirt or dust, including yard work, gardening, and digging.
  • Use air filtration measures indoors.
  • Clean skin injuries well with soap and water to reduce the chances of developing a skin infection, especially if the wound was exposed to dirt or dust.
  • Take preventive antifungal medication if your healthcare provider says you need it.
Coccidioides immitis on Sabouraud's medium
Coccidioides immitis on Sabouraud's medium

Life Cycle of Coccidioides

Coccidioides spores circulate in the air after contaminated soil and dust are disturbed by humans, animals, or the weather. The spores are too small to see without a microscope. When people breathe in the spores, they are at risk for developing Valley fever. After the spores enter the lungs, the person’s body temperature allows the spores to change shape and grow into spherules. When the spherules get large enough, they break open and releases smaller pieces (called endospores) which can then potentially spread within the lungs or to other organs and grow into new spherules.


Healthcare providers rely on your medical and travel history, symptoms, physical examinations, and laboratory tests to diagnose Valley fever. The most common way that healthcare providers test for Valley fever is by taking a blood sample and sending it to a laboratory to look for Coccidioides antibodies or antigens.

Healthcare providers may do imaging tests such as chest x-rays or CT scans of your lungs to look for Valley fever pneumonia. They may also perform a tissue biopsy, in which a small sample of tissue is taken from the body and examined under a microscope. Laboratories may also see if Coccidioides will grow from body fluids or tissues (this is called a culture).

Skin testing

A skin test can detect whether you have developed an immune response to the fungus Coccidioides, the cause of Valley fever. This test became available again in the United States in 2014 for the first time since the late 1990s. Your healthcare provider might do this test if you have a history of Valley fever.



For many people, the symptoms of Valley fever will go away within a few months without any treatment. Healthcare providers choose to prescribe antifungal medication for some people to try to reduce the severity of symptoms or prevent the infection from getting worse. Antifungal medication is typically given to people who are at higher risk for developing severe Valley fever. The treatment is usually 3 to 6 months of fluconazole or another type of antifungal medication. There are no over-the-counter medications to treat Valley fever. If you have Valley fever, you should talk to your healthcare provider about whether you need treatment. The healthcare provider who diagnoses you with Valley fever may suggest that you see other healthcare providers who specialize in treating Valley fever.

People who have severe lung infections or infections that have spread to other parts of the body always need antifungal treatment and may need to stay in the hospital. For these types of infections, the course of treatment is usually longer than 6 months. Valley fever that develops into meningitis is fatal if it’s not treated, so lifelong antifungal treatment is necessary for those cases.


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