Valley fever is a fungal infection caused by coccidioides (kok-sid-e-OY-deze) organisms. It can cause signs and symptoms such as a fever, cough and tiredness.

Two coccidioides fungi species cause valley fever. These fungi are commonly found in soil in specific regions. The fungi's spores can be stirred into the air by anything that disrupts the soil, such as farming, construction and wind.

People can then breathe the fungi into their lungs. The fungi can cause valley fever, also known as acute coccidioidomycosis (kok-sid-e-oy-doh-my-KOH-sis). Mild cases of valley fever usually resolve on their own. In more-severe cases, doctors treat the infection with antifungal medications.


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 lower legs but sometimes on the chest, arms and back

If you don't become ill or have symptoms from valley fever, you may only find out you've been infected later. You may find out when you have a positive skin or blood test or when small areas of residual infection in the lungs (nodules) show up on a routine chest X-ray. The nodules typically don't cause problems, but they can look like cancer on X-rays.

If you develop symptoms, especially severe ones, the course of the disease is highly variable. It can take months to fully recover. Fatigue and joint aches can last even longer. The disease's severity depends on several factors, including your overall health and the number of fungus spores you inhale.

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 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 initial infection
  • 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

When to see a doctor

Seek medical care if you are over 60, have a weakened immune system, are pregnant, or are of Filipino or African heritage, and you develop the signs and symptoms of valley fever, especially if you:

  • Live in or have recently traveled to an area where this disease is common
  • Have symptoms that aren't improving

Be sure to tell your doctor if you've traveled to a place where valley fever is common and you have symptoms.


Valley fever is caused by a person inhaling spores of certain fungi. The fungi that cause valley fever — Coccidioides immitis or Coccidioides posadasii — live in the soil in parts of Arizona, Nevada, Utah, New Mexico, California, Texas and Washington. It's named after the San Joaquin Valley in California. The fungi can also often be found in northern Mexico and Central and South America.

Like many other fungi, coccidioides species have a complex life cycle. In the soil, they grow as a mold with long filaments that break off into airborne spores when the soil is disturbed. A person can then inhale the spores.

The spores are extremely small and can be carried far by the wind. Once inside the lungs, the spores reproduce, continuing the disease cycle.

Risk factors

Risk factors for valley fever include:

  • Environmental exposure. Anyone who inhales the spores that cause valley fever is at risk of infection. People who live in areas where the fungi are common — especially those who spend a lot of time outdoors — have a greater risk.

    Also, people who have jobs that expose them to dust are most at risk — construction, road and agricultural workers, ranchers, archaeologists, and military personnel on field exercises.

  • Race. For reasons that aren't well understood, people of Filipino and African heritage are more susceptible to developing serious fungal infections.
  • Pregnancy. Pregnant women are vulnerable to more-serious infections when they get the infection during the third trimester. New mothers are vulnerable right after their babies are born.
  • Weakened immune system. Anyone with a weakened immune system is at increased risk of serious complications. This includes people living with acquired immunodeficiency syndrome (AIDS) or those being treated with steroids, chemotherapy and anti-rejection drugs after transplant surgery. People with certain autoimmune diseases, such as rheumatoid arthritis or Crohn's disease, who are being treated with anti-tumor necrosis factor (TNF) drugs also have an increased risk of infection.
  • Diabetes. People with diabetes may have a higher risk of severe lung infections.
  • Age. Older adults are more likely to develop valley fever. This may be because their immune systems are less robust or because they have other medical conditions that affect their overall health.


Some people, especially pregnant women, people with weakened immune systems — such as those living with human immunodeficiency virus (HIV)/AIDS — and those of Filipino or African heritage are at risk of developing a more severe form of coccidioidomycosis.

Complications of coccidioidomycosis may include:

  • Severe pneumonia. Most people recover from coccidioidomycosis-related pneumonia without complications. Others, such as people of Filipino and African heritage, and those with weakened immune systems, may become seriously ill.
  • Ruptured lung nodules. A small percentage of people develop thin-walled nodules (cavities) in their lungs. Many of these eventually disappear without causing any problems, but some may rupture, causing chest pain and difficulty breathing. A ruptured lung nodule might require the placement of a tube into the space around the lungs to remove the air or surgery to repair the damage.
  • Disseminated disease. This is the most serious complication of coccidioidomycosis but it's uncommon. If the fungus spreads (disseminates) throughout the body, it can cause problems including skin ulcers, abscesses, bone lesions, severe joint pain, heart inflammation, urinary tract problems and meningitis — a potentially fatal infection of the membranes and fluid covering the brain and spinal cord.


There is no vaccine to prevent valley fever.

If you live in or visit areas where valley fever is common, take common-sense precautions, especially during the dry season following a rainy season when the chance of infection is highest.

Consider these tips:

  • Wear a mask.
  • Avoid very dusty areas, such as construction sites.
  • Stay inside during dust storms.
  • Wet the soil before digging in it, or avoiding soil if you're at higher risk of infection.
  • Keep doors and windows tightly closed.
  • Clean skin injuries with soap and water.

Mar 21, 2023

  1. Valley fever (coccidioidomycosis). Centers for Disease Control and Prevention. https://www.cdc.gov/fungal/diseases/coccidioidomycosis/index.html. Accessed July 9, 2020.
  2. Ferri FF. Coccidioidomycosis. In: Ferri's Clinical Advisor 2020. Elsevier; 2020. https://www.clinicalkey.com. Accessed July 8, 2020.
  3. Blair JE, et al. Pulmonary primary coccidioidal infection. https://www.uptodate.com/contents/search. Accessed July 9, 2020.
  4. Coccidioidomycosis. In: Elsevier Point of Care. Elsevier; 2020. https://www.clinicalkey.com. Accessed July 8, 2020.
  5. AskMayoExpert. Coccidioidomycosis. Mayo Clinic; 2020.
  6. Jameson JL, et al., eds. Coccidioidomycosis. In: Harrison's Principles of Internal Medicine. 20th ed. The McGraw-Hill Companies; 2018. https://accessmedicine.mhmedical.com. Accessed July 9, 2020.
  7. Bennett JE, et al. Coccidioidomycosis (Coccidioidies species). In: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed July 9, 2020.
  8. Valley fever (coccidioidomycosis) statistics. Centers for Disease Control and Prevention. https://www.cdc.gov/fungal/diseases/coccidioidomycosis/statistics.html. Accessed March 1, 2023.
  9. Huff D, et al. Coccidioidomycosis and COVID-19 infection. An analysis from a single medical center within the coccidioidal endemic area. Mycopathologia. 2022; doi:10.1007/s11046-022-00629-6.
  10. Jugler C, et al. Humanization and expression of IgG and IgM antibodies in plants as potential diagnostic reagents for valley fever. Frontiers in Plant Science. 2022; doi:10.3389/fpls.2022.925008.
  11. Coccidioidomycosis clinical trials at Mayo Clinic. Mayo Clinic; 2023. https://www.mayo.edu/research/clinical-trials/search-results?keyword=coccidioidomycosis&studySiteStatusesGrouped=Open/Status%20Unknown. Accessed Jan. 30, 2023.
  12. Vallabhaneni S, et al. The global burden of fungal diseases. Infectious Disease Clinics of North America. 2016; doi: 10.1016/j.idc.2015.10.004.
  13. O'Shaughnessy E, et al. FDA public workshop summary — Coccidioidomycosis (valley fever): Considerations for development of antifungal drugs. Clinical Infectious Diseases. 2022; doi:10.1093/cid/ciab904.
  14. Nguyen HT. Allscripts EPSi. Mayo Clinic. Feb. 28, 2023.
  15. Brewer AC, et al. Cutaneous effects associated with fluconazole in patients treated for coccidioidomycosis. International Journal of Dermatology. 2019; doi:10.1111/ijd.14238.


Double your impact on fighting cancer

Make a gift before July 31 and it can go twice as far to fight cancer.