What Is Coccidiodomycosis (Valley Fever)?

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Coccidioidomycosis, a fungal infection caused by Coccidioides immitis or Coccidioides posadaii, is commonly known as "Valley Fever." It is endemic to parts of the Southwest United States. from Texas to southern California as well as northern Mexico, Central America, and South America. While coccidioidomycosis primarily affects the lungs, it is considered an AIDS-defining illness when it spreads (disseminates) beyond the lungs.

Coccidiomycosis symptoms
Illustration by Emily Roberts, Verywell

Coccidioidomycosis Symptoms

Most people with coccidioidomycosis will not experience symptoms as their immune systems are strong enough to control the infection. Of those that do experience symptoms, the most common symptoms tend to be mild and flu-like, including:

  • Fever
  • Headache
  • Cough
  • Fatigue
  • Chest pain
  • Chills
  • Shortness of breath (dyspnea)
  • Muscle pain (myalgia)
  • Joint pain (arthralgia)

 A rash on the upper body or legs is also a common symptom. Coccidioidomycosis is a common cause of community-acquired pneumonia in the southwest United States.

In rare cases, coccidioidomycosis can become serious, causing deep scars and cavities in the lungs.

Once disseminated, it can affect multiple organ systems. Complications can include:

  • Skin ulcers and abscesses
  • Swollen and painful joints
  • Bone lesions
  • Heart inflammation
  • Urinary tract problem
  • Meningitis

Meningitis is fatal if it is not treated. Approximately 5% to 10% of people who get Valley Fever will develop serious or long-term problems in their lungs.


The Coccidioides fungus is present in the soil and can produce airborne spores during the rainy season. Infection is caused by inhaling the spores, usually without the person even knowing it.

Once inside the lungs, the fungal spores can multiply and create eruptive nodules in the airways. In people with severe immune supression—particularly those diagnosed with AIDS—this lead to severe lung infections. Without the immune defenses to stop it, the fungus can spread to the blood and cause disease in distant organs. Coccidioides cannot be passed from person to person.


In 2017, there were 14,364 cases of Valley fever reported to the Centers for Disease Control and Prevention (CDC). The majority of infections occur in Arizona and California. In Phoenix and Tucson, for example, Valley Fever causes an estimated 15% to nearly 30% of community-acquired pneumonias, but low testing rates suggest that Valley fever is probably under-recognized.

In 2011, more than 22,000 new cases of coccidioidomycosis were reported by the CDC. In 2017, the number of cases decreased to slightly more than 14,000. On average, there were approximately 200 coccidioidomycosis-associated deaths each year in the United States between 1999–2016.

The incidence and severity of coccidioidomycosis has decreased in people with HIV due to the widespread use of antiretroviral therapy.


Coccidioidomycosis can be diagnosed by microscopic examination of body fluids (such as sputum) or tissue samples from the lungs. The samples can also be cultured in the lab as evidence of infection.

In addition, there are blood tests that can detect immune proteins, called antibodies, that are produced by the body in response to the infection. Another test, called the polymerase chain reaction (PCR), can confirm the infection by amplifying the fungi's genetic material.

Chest X-rays may be used to support the diagnosis.


For people with an intact immune system, coccidioidomycosis is generally self-limiting and requires no treatment other than supportive care (such as pain relievers and bed rest).

For those requiring treatment—either because of persistent symptoms or progressive disease—oral antifungals are considered the first-line choice.

Fluconazole is the most frequently prescribed oral antifungal drug for uncomplicated coccidioidal pneumonia because it is predictably well absorbed, has fewer drug interactions, and is least expensive when compared to other azole options. Antifungal therapy should be considered for pregnant women, however, treatment depends on the stage of pregnancy. 

For the severely ill, the antifungal amphotericin B is considered the drug of choice. It would be delivered intravenously until the infection is controlled, after which life-long oral antifungals prescribed would be prescribed to prevent recurrence.

For people with Coccidioides-related meningitis, amphotericin B can be administered intrathecally (into the space that surrounds either the brain or spinal cord).


It is difficult to prevent coccidioidomycosis in areas where the fungus is endemic. For people with severely compromised immune systems, prophylactic (preventive) antifungal therapy is not recommended, though yearly or twice-yearly testing is recommended. No vaccines are available to prevent coccidioidomycosis.

If you live an endemic region, like California or Arizona, and believe yourself to at risk, there are a few precautions you can take.

Tips to Prevent Coccidioimycosis

  • Wear a dust mask when working with soil, or water down the soil to reduce airborne fungus.
  • Avoid going outside during a dust storm or high winds.
  • Use air quality measures, such as a HEPA filter, and install inexpensive window and door seals.
  • If working at a construction site, wear an N95 particle filtering mask.

A Word From Verywell

Coccidioidomycosis, known as Valley Fever, is most common in the Southwest United States. The condition poses the biggest threat to people with compromised immune systems (particularly if you have HIV). The symptoms may be mild and flu-like. Though most people do not require treatment as their immune systems can fight the disease, for those who need treatment, oral antifungals are generally the first line of response. Speak with your healthcare provider if you are experiencing symptoms or you are concerned about your susceptibility to coccidioidomycosis.

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7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Symptoms of Valley Fever (Coccidioidomycosis). Reviewed January 2, 2019.

  2. Malo J, Luraschi-monjagatta C, Wolk DM, Thompson R, Hage CA, Knox KS. Update on the diagnosis of pulmonary coccidioidomycosis. Ann Am Thorac Soc. 2014;11(2):243-53. doi:10.1513/AnnalsATS.201308-286FR

  3. Centers for Disease Control and Prevention. Treatment for Valley Fever (Coccidioidomycosis). Reviewed January 2, 2019.

  4. Centers for Disease Control and Prevention. Valley Fever (Coccidioidomycosis) Risk & Prevention. Reviewed January 2, 2019

  5. Centers for Disease Control and Prevention. Valley Fever (Coccidioidomycosis) Statistics. Reviewed January 4, 2019.

  6. U.S. Department of Health and Human Services. AIDSinfo. Coccidioidomycosis. Reviewed June 26, 2019.

  7. Galgiani JN, Ampel NM, Blair JE, et al. 2016 Infectious Diseases Society of America (IDSA) Clinical Practice Guideline for the Treatment of Coccidioidomycosis. Clin Infect Dis. 2016;63(6):e112-46. doi:10.1093/cid/ciw360

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