Valley fever is an infection caused by the fungus Coccidioides. The scientific name for Valley fever is “coccidioidomycosis,” and it’s also sometimes called “San Joaquin Valley fever” or “desert rheumatism.” The term “Valley fever” usually refers to Coccidioides infection in the lungs, but the infection can spread to other parts of the body in severe cases (this is called “disseminated coccidioidomycosis”).


Coccidioidomycosis is caused by two distinct Coccidiodies species of soil fungus, Coccidioides immitis and Coccidioides posadaii.

The infection occurs through:

  • Inhalation of spores during outdoor activities (most common)
  • Puncture wounds with infected objects
  • Organ transplantation or sexual transmission from an infected individual (rare)


Valley fever is the initial form of coccidioidomycosis infection. This initial, acute illness can develop into a more serious disease, including chronic and disseminated coccidioidomycosis.

Acute coccidioidomycosis (valley fever)

The initial, or acute, form of coccidioidomycosis is often mild, with few or no symptoms. Signs and symptoms occur one to three weeks after exposure. They tend to be similar to flu symptoms. Symptoms can range from minor to severe, including:

  • Fever
  • Cough
  • Tiredness
  • Shortness of breath
  • Headache
  • Chills
  • Night sweats
  • Joint aches and muscle soreness
  • Red, spotty rash, mainly on the lower legs but sometimes on the chest, arms, and back

Chronic coccidioidomycosis

If the initial coccidioidomycosis infection doesn't completely resolve, it may progress to a chronic form of pneumonia. This complication is most common in people with weakened immune systems.

Signs and symptoms include:

  • Low-grade fever
  • Weight loss
  • Cough
  • Chest pain
  • Blood-tinged sputum (matter discharged during coughing)
  • Nodules in the lungs

Disseminated coccidioidomycosis

The most serious form of the disease, disseminated coccidioidomycosis, is uncommon. It occurs when the infection spreads (disseminates) beyond the lungs to other parts of the body. Most often these parts include the skin, bones, liver, brain, heart, and the membranes that protect the brain and spinal cord (meninges).

Signs and symptoms of the disseminated disease depend on the body parts affected and may include:

  • Nodules, ulcers, and skin lesions that are more serious than the rash that sometimes occurs with other forms of the disease
  • Painful lesions in the skull, spine, or other bones
  • Painful, swollen joints, especially in the knees or ankles
  • Meningitis - an infection of the membranes and fluid surrounding the brain and spinal cord


To diagnose Valley fever, your healthcare provider may order some or all of these tests:

  • Blood tests: Blood tests are the most common way to diagnose Valley fever. Your provider uses a needle to take blood from your vein, which they then send to a lab to look for certain signs of coccidioides (antibodies or antigens).
  • Biopsy: Your provider may take a small amount of tissue and send it to a lab to look for signs of coccidioides.
  • Imaging: Your provider may use a chest X-ray or CT scan to look for Valley fever pneumonia, a potentially serious complication. This will give your provider pictures of your lungs to see if there are any changes that indicate pneumonia.

General Rating Formula for Mycotic Lung Disease (diagnostic codes 6834 through 6839):

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