Coccidioidomycosis (Valley Fever)

Coccidioidomycosis (kok-sih-dee-oyd-o-my-KO-sis), also know as valley fever, is a disease that can occur after breathing in the spores * of a fungus found naturally in the soil of dry regions, such as the southwestern United States.


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Coccidioides immitis

Desert rheumatism

Fungal infection

San Joaquin Valley fever

What Is Coccidioidomycosis?

During World War II, American trainees sent to Arizona and parts of southern California for flight training took thousands of days of sick leave because of coccidioidomycosis, a disease caused by Coccidioides immitis (kok-sih-dee-OYD-eez IH-mih-tus), a fungus that hibernates a few inches beneath semi-dry soil. The disease's other name, valley fever, comes from the San Joaquin Valley region of California, where the fungus was first identified.

After regular rainfall, the coccidioides fungus blooms into tiny mold spores. If the soil is stirred by events such as dust storms, earthquakes, farming, excavation, or construction work, these microscopic spores spring into the air, where they are easily breathed into the lungs of people and animals.

* spores are a temporarily inactive form of a germ enclosed in a protective shell.

Coccidioidomycosis cannot be passed from person to person. People must inhale the spores of the fungus in order to contract the disease. Most people who inhale the spores develop only a mild case of disease, in which the infection results in symptoms similar to those of a cold or the flu that go away on their own. Many people are not even aware that they are infected when the symptoms are mild. For those with weakened immune systems and for people of African or Filipino ancestry (who, for some unknown reason, get more severe forms of the disease), coccidioidomycosis can be much more serious, spreading from the lungs to other parts of the body and even to the brain. Severe cases may result in meningitis * . Coccidioides infection that has spread throughout the body and occurs with arthritis * is sometimes called desert rheumatism (ROO-muh-tih-zum). In general, the more fungal spores inhaled by a person, the more serious the disease tends to be.

Is Coccidioidomycosis Common?

The fungus that causes coccidioidomycosis is found mainly in the desert climates of the southwestern United States, parts of Mexico, and Central and South America. The infection is considered endemic * in these regions. People who live in or visit "cocci country" and who often spend time outside for work or play are more likely to develop the disease, especially near areas of development and construction during the summer and fall. Up to 50 percent of people living in such areas have antibodies * against Coccidioides immitis in their blood, which indicates that they have been exposed to the fungus, although many of them never developed signs of the disease.

Signs and symptoms

About 60 percent of people infected by Coccidioides immitis develop no symptoms. When symptoms do occur, they are usually mild and include fever, aches, chills, headache, and tiredness. Those with weakened immune systems, such as people with AIDS, certain types of cancer, and diabetes, have a greater risk of developing a more severe form of the infection.


A doctor diagnoses coccidioidomycosis by culturing * a patient's sputum * or by doing a skin test. If injecting the test material into the skin of the forearm causes a large circular welt to appear on the arm within 2 days, it is considered a positive test for the fungus. Blood tests may show antibodies to the fungus, which helps confirm the diagnosis. A chest X ray is sometimes taken to look for signs of infection or inflammation in the lungs.


Most mild cases of the disease can be managed with bed rest, over-the-counter pain relievers such as acetaminophen (uh-see-teh-MIH-noh-fen), and sometimes oral (by mouth) anti-fungal medication. In more serious cases in which the fungus has spread throughout the body, intravenous (in-tra-VEE-nus, or given directly into a vein) antifungal medicines and hospitalization may be necessary. Mild cases of coccidioidomycosis last about 2 weeks, but recovery may take up to 6 months in more severe cases.

* meningitis (meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.

* arthritis (ar-THRY-tis) refers to any of several disorders characterized by inflammation of the joints,

* endemic (en-DEH-mik) describes a disease or condition that is present in a population or geographic area at all times.

* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

* culturing (KUL-chur-ing) means subjecting to a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified,

* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.

* pneumonia (nu-MO-nyah) is inflammation of the lung.


Pneumonia * , arthritis, meningitis, and other serious problems can result if the infection spreads throughout the lungs or to other parts of the body, such as the liver, heart, brain, bones, or joints.

Can Coccidioidomycosis Be Prevented?

No specific activities can prevent a person from becoming infected with the coccidioides fungus, other than avoiding the regions where it is found. Planting grass and paving roads may reduce dust in problem areas but will not kill the fungus.

See also
Arthritis, Infectious
Fungal Infections



U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC offers information about coccidioidomycosis at its website.
Telephone 800-311-3435

U S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894. The National Library of Medicine has a website packed with information on diseases (including coccidioidomycosis) and drugs, consumer resources, dictionaries and encyclopedias of medical terms, and directories of doctors and helpful organizations.
Telephone 888-346-3656

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