An Overview of 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


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 will develop in around 25 percent of cases and will usually be isolated to the lower extremities. Moreover, between 5 and 8 percent of cases will develop pneumonia, although it will usually resolve without treatment.

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 by far the most serious complication. While the overall mortality rate is low (.07 percent), for those with advanced HIV infection, as many as 70 percent of infections will result in death even with appropriate treatment.


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.


According to the Centers for Disease Control and Prevention (CDC), the incidence of coccidioidomycosis in the United States is 44 cases per 100,000 people. The majority of infections occur in Arizona and California, where the incidence can run as high as 248 cases per 100,000.

In 2011, over 22,000 new cases of coccidioidomycosis were reported by the CDC, a ten-fold increase from 1998. In California alone, the number increased from 719 in 1998 to a high of 5,697 in 2011.

Despite the upswing in infections, the incidence of symptomatic 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.

While ketoconazole is the only approved option for the treatment of coccidioidomycosis, many doctors find that fluconazole or itraconazole are equally effective. While generally safe for use, antifungals like ketoconazole, fluconazole, and itraconazole are contraindicated during pregnancy as they have the potential to cause birth defects during the first trimester.

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 may be used to avoid infection. 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

Coccidioimycosis, 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 doctor if you are experiencing symptoms or you are concerned about your susceptibility to Coccidioimycosis.

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