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(San Joaquin Fever; Valley Fever)


Paschalis Vergidis

, MD, MSc, Mayo Clinic College of Medicine & Science

Reviewed/Revised Nov 2023
Topic Resources

Coccidioidomycosis is an infection, usually of the lungs, caused by the fungus Coccidioides immitis or Coccidioides posadasii.

  • 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.

  • Treatment is with antifungal medications.

The spores of Coccidioides are present in soil in the southwestern United States, the central valley of California, parts of New Mexico, Texas west of El Paso, northern Mexico, and parts of Central America and Argentina. They also can be found in Utah, Nevada, and southcentral Washington.

Coccidioidomycosis causes about 15 to 30% of cases of community-acquired pneumonia Community-Acquired Pneumonia Community-acquired pneumonia is lung infection that develops in people who are not patients in a hospital, usually in people with a normal (competent) immune system, or in those who are immunocompromised... read more (a lung infection that develops in people who are not patients in a hospital) in metropolitan areas of Arizona such as Tucson and Phoenix.

In the United States, 20,003 cases of coccidioidomycosis were reported in 2019.

Coccidioidomycosis is acquired by inhaling spores. Spores are present in soil and can become airborne when the soil is disturbed and dust travels downwind. 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:

  • Acute primary coccidioidomycosis is a mild lung infection. The infection disappears without treatment. This form accounts for most cases.

  • Progressive coccidioidomycosis is a severe, rapidly worsening infection. 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. Risk factors include

Symptoms of Coccidioidomycosis

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.

People with progressive coccidioidomycosis may develop symptoms 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 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 Subacute and Chronic Meningitis Subacute meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space) when it develops... read more . This infection is often chronic, causing headaches, confusion, loss of balance, double vision, and other problems. Untreated meningitis is always fatal.

Diagnosis of Coccidioidomycosis

  • Blood tests

  • A chest x-ray

  • Examination and culture 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, cerebrospinal fluid, 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.

Treatment of Coccidioidomycosis

  • Antifungal medications

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 medication, such as fluconazole.

Progressive coccidioidomycosis is usually fatal unless it is treated, particularly if the immune system is weakened. About 70% of people with severe HIV infection or 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 progressive coccidioidomycosis, amphotericin B is given intravenously.

Doctors do not give certain antifungal medications to pregnant people in the first trimester of pregnancy because they may cause birth defects. People with mild to moderate coccidioidomycosis who are in the first trimester typically do not require treatment. However, doctors may give amphotericin B to pregnant people who are in the first trimester and who have a severe coccidioidomycosis infection or an infection that has spread beyond their lungs. After the first trimester, doctors may give a different antifungal medication. Pregnant people who become infected in the second or third trimester or within 6 weeks of giving birth are at risk of having the infection progress. If these people are not treated with medications, doctors follow up with them and do blood tests to determine whether the infection spreads.

If meningitis develops, fluconazole is given. People who have had meningitis due to coccidioidomycosis must take fluconazole for the rest of their life because relapses are common and potentially fatal.

People with a weakened immune system must take medications for years, often for life.

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

Drugs Mentioned In This Article

Generic Name Select Brand Names
Amphocin, Fungizone
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