Coccidioidomycosis (Valley Fever)

Infectious Agent

The fungi Coccidioides immitis and C. posadasii .


Through inhalation of fungal conidia from the environment. Not transmitted from person to person.


Endemic in the western United States, particularly Arizona and Southern California, and parts of Mexico and Central and South America. Travelers are at increased risk if they participate in activities that expose them to soil disruption and outdoor dust. Outbreaks have been associated with activities such as construction, archaeological excavation, and military training exercises.

Clinical Presentation

The incubation period is 7–21 days. Most infections (60%) are asymptomatic. Symptomatic infection ranges from primary pulmonary illness to severe disseminated disease. Primary pulmonary coccidioidomycosis is characterized by fatigue, cough, fever, shortness of breath, headache, night sweats, muscle aches, joint pain, and rash. These infections are often self-limited, and symptoms typically resolve in a few weeks to months. However, 5%–10% of people go on to develop serious or chronic lung disease, such as cavitary pneumonia, fibrosis, and bronchiectasis. In rare instances (approximately 1% of infections), dissemination to the central nervous system, joints, bones, or skin may occur.

Older people (≥65 years), people with diabetes, and people who smoke are at increased risk of developing severe pulmonary complications. People with depressed cellular immune function, pregnant women, and people of African American or Filipino descent are at increased risk of developing disseminated disease.


The methods most commonly used to diagnose coccidioidomycosis are serology, culture, histopathology, and molecular techniques. EIA is a sensitive serologic method to detect IgM and IgG. Immunodiffusion and complement fixation can also detect antibodies and are often used to confirm diagnosis. Lateral flow assays to detect any antibodies in serum became available in 2018. Isolation of Coccidioides from fungal culture of respiratory specimens or tissue provides a definitive diagnosis. Microscopy of sputum or tissue can identify Coccidioides spherules but has low sensitivity. Molecular techniques include DNA probe for confirmation of cultures, as well as PCR for direct detection from clinical specimens, which became available in early 2018. Coccidioidomycosis is a nationally notifiable disease in the United States.


Expert opinions differ on the proper management of patients with uncomplicated primary pulmonary disease in the absence of risk factors for severe or disseminated disease. Some experts recommend no therapy since most illnesses are self-limited, whereas others advise treatment to reduce the intensity or duration of symptoms. Treatment with antifungal agents has not been proven to prevent dissemination. People at high risk for dissemination and people with the following clinical manifestations should receive antifungal therapy:

  • Severe acute pulmonary disease
  • Chronic pulmonary disease
  • Disseminated disease

Depending on the clinical situation, a variety of antifungal agents may be used.


Limit exposure to outdoor dust in endemic areas.

CDC website:


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Orion Z. McCotter, Tom M. Chiller