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(San Joaquin Fever; Valley Fever)


Sanjay G. Revankar

, MD, Wayne State University School of Medicine

Last full review/revision Sep 2019| Content last modified Sep 2019
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Coccidioidomycosis is infection, usually of the lungs, caused by the fungus Coccidioides immitis.

  • The infection is caused by inhaling spores of the fungus.

  • If mild, the lung infection causes flu-like symptoms and sometimes shortness of breath, but the infection may worsen and spread throughout the body, causing various symptoms.

  • The diagnosis can be confirmed by identifying the fungi in samples of infected materials examined under a microscope or cultured.

  • Antifungal drugs are usually taken for 6 to 12 months but sometimes for life.

The spores of Coccidioides are present in soil in the southwestern United States, the central valley of California, northern Mexico, parts of Central America, and Argentina. About 30 to 60% of people who live in one of these areas are exposed to the fungus at some point during their life. In the United States, 14,364 cases of coccidioidomycosis were reported in 2017.

Farmers and others who work with or are exposed to disturbed soil are most likely to inhale the spores and become infected. People who become infected while traveling may not develop symptoms until after they go home.

Coccidioidomycosis occurs in two forms:

  • Mild lung infection (acute primary coccidioidomycosis): The infection disappears without treatment. This form accounts for most cases.

  • Severe, progressive infection (progressive coccidioidomycosis): The infection spreads from the lungs throughout the body and is often fatal.

Risk factors for progressive coccidioidomycosis

Progressive coccidioidomycosis is uncommon in otherwise healthy people. It is more likely to occur when people

  • Use drugs that suppress the immune system (immunosuppressants)

  • Are older

  • Are in the second half of their pregnancy or just had a baby

  • Have certain ethnic backgrounds (Filipino, African American, Native American, Hispanic, and Asian, in decreasing order of risk)


Most people with acute primary coccidioidomycosis have no symptoms. If symptoms develop, they appear 1 to 3 weeks after people are infected. Symptoms are usually mild and often flu-like. They include a cough, fever, chills, chest pain, and sometimes shortness of breath. The cough may produce sputum. Occasionally, when lung infection is severe, spaces may form in the lungs and people may cough up blood.

Some people have an allergic reaction to the fungus, which can cause joint pain, conjunctivitis, tender red or violet bumps (nodules) under the skin (called erythema nodosum), or patches of red, raised skin that often look like targets (erythema multiforme).

The progressive form may develop weeks, months, or even years after the initial infection. Symptoms include mild fever and loss of appetite, weight, and strength. The lung infection may worsen, usually only in people with a weakened immune system. It may cause increased shortness of breath and sometimes blood in the sputum.

Coccidioidomycosis may also spread from the lungs to the skin, bones (causing osteomyelitis), joints, liver, spleen, kidneys, and other tissues. If infection spreads to the skin, people may have one sore or many. Joints may become swollen and painful. Deep infections sometimes break through the skin, causing an opening that infected material drains through.

Coccidioides can also infect the brain and the tissues covering the brain (meninges), causing meningitis. This infection is often chronic, causing headaches, confusion, loss of balance, double vision, and other problems. Untreated meningitis is always fatal.


  • Blood tests

  • A chest x-ray

  • Examination, culture, or testing of a sample of blood or other tissue

A doctor may suspect coccidioidomycosis if people develop symptoms after living in or recently traveling through an area where the infection is common.

Blood tests to detect antibodies to the fungus (serologic tests) and a chest x-ray are typically done. In people with a healthy immune system, blood tests can usually detect these antibodies if coccidioidomycosis is present. Chest x-rays usually show characteristic abnormalities. These findings help doctors make the diagnosis.

A test that detects antigens (proteins released by the fungus) in urine may also be useful.

To identify the fungus and thus confirm the diagnosis, doctors may examine samples of blood, sputum, pus, or other infected tissue under a microscope or send them to a laboratory to be cultured. Because culturing Coccidioides may take up to 3 weeks, doctors typically rely on the blood tests and chest x-ray. A test to identify the fungus' genetic material (its DNA) can be done on samples taken from the throat and lungs, but this test is not widely available.


  • Antifungal drugs

Acute primary coccidioidomycosis typically goes away without treatment in otherwise healthy people, and recovery is usually complete. However, some doctors prefer to treat such people because of the small chance that the coccidioidomycosis will spread. Also, when people are treated, symptoms resolve more quickly. Treatment is usually with an antifungal drug, such as fluconazole, for 3 to 6 months.

Progressive coccidioidomycosis is usually fatal unless it is treated, particularly if the immune system is weakened. About 70% of people with AIDS die within 1 month after being diagnosed. For mild to moderate progressive coccidioidomycosis, fluconazole or itraconazole is given by mouth. Alternatively, the doctor may treat the infection with voriconazole, given by mouth or by vein (intravenously), or posaconazole, given by mouth. For severe cases, amphotericin B is given intravenously.

If meningitis develops, fluconazole is given. People who have had meningitis due to coccidioidomycosis must take fluconazole for the rest of their life.

Although drug treatment can be effective in localized infections (for example, in the skin, bones, or joints), relapses often occur after treatment is stopped. Usually, people with a weakened immune system must take drugs for years, often for life.

If bone is infected or if the infection results in spaces in the lung, surgery may be necessary.

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