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Valley fever, or coccidioidomycosis, is a respiratory infection caused by a fungus called Coccidioides that lives in dry soil in the southwestern United States and other areas of the world. According to the Centers for Disease Control and Prevention (CDC), cases of valley fever increased from 2,265 in 1998 to more than 22,000 in 2011 in Arizona, California, Nevada, New Mexico and Utah.

Although most people exposed to Coccidioides (between 30 and 60 percent of people who live in areas where the fungus is common) do not get sick, the CDC reports that 75 percent of those who do become ill miss school or work—usually for about 2 weeks—and more than 40 percent require hospitalization. Valley fever causes symptoms similar to those caused by the flu (influenza) or pneumonia, often lasting weeks or months.

Valley Fever Risk

People with a weakened immune system (for example, those with HIV), people of African American or Filipino decent, and women who are in their third trimester of pregnancy are at increased risk for serious infection and complications from valley fever. Early diagnosis and treatment is especially important in these people. Animals, including pets, also can develop coccidioidomycosis.

More research is needed to determine why cases of valley fever have increased so dramatically in recent years. The increase may be related to changes in weather patterns affecting where the fungus grows, how much is present in the soil, and how much is circulating in the air. While infection has been reported in 28 states and Washington D.C., only about 1 percent of all cases occur in states outside of those mentioned above.

Valley Fever Symptoms

Symptoms of valley fever usually develop between 1 and 3 weeks of exposure. For most people, symptoms are mild and resolve on their own without treatment. In severe cases, symptoms may linger for 6 months or longer without prompt diagnosis and treatment.

Coccidioidomycosis symptoms include the following:

  • Cough
  • Fever
  • Headache
  • Joint pain (knees, ankles)
  • Muscle aches
  • Rash (trunk, arms, legs)

Symptoms of severe infection include:

  • Bone/joint infection
  • Chronic pneumonia
  • Meningitis (inflammation of the covering surrounding the brain and spinal cord)
  • Skin lesions

Valley Fever Diagnosis

If your health care provider suspects valley fever, a medical history (including evaluating possible exposure through travel to an endemic area), physical examination, and laboratory tests—such as blood and urine tests to detect Coccidioides antibodies, cultures to detect the fungus, and imaging tests like chest x-rays—can be used to confirm the diagnosis. In some cases, a tissue biopsy also may be performed.

Once you've had coccidioidomycosis, your immune system develops antibodies to prevent future infection. However, some people experience a relapse after seeming to improve. Rarely, valley fever can cause long-term complications, such as chronic pneumonia or neurological damage.

Valley Fever Treatment & Prevention

More studies are needed to determine the best way to treat valley fever and develop a vaccine to prevent infection. Although most cases do not require medical treatment, anti-fungal medications like fluconazole can help prevent and treat complications. Serious infections may also require respiratory therapy or hospitalization.

Valley fever does not spread from person to person, animal to animal, or animal to human—the fungus spreads through the air, so it can be very difficult to avoid exposure in areas where it is common. The CDC recommends avoiding activities like yard work, gardening, and digging in endemic areas, as well as staying away from dusty environments like construction sites as much as possible.

Other preventative measures include wearing a mask to filter out airborne particles (e.g., N95 mask), using a HEPA filter, cleaning skin injuries thoroughly—especially if exposed to soil or dust, and taking anti-fungal medications as recommended by your doctor.

If you live in or have recently traveled to the southwestern United States, Mexico, or South America, and develop flu-like symptoms that last longer than 1 week, contact your health care provider. Prompt treatment can help prevent complications of valley fever.

Source: Centers for Disease Control and Prevention (CDC)

Publication Review By: the Editorial Staff at

Published: 08 Apr 2013

Last Modified: 05 Jan 2015