Reducing Risk for Valley Fever

Key points

  • Valley fever is caused by breathing in spores from the fungus Coccidioides.
  • Coccidioides lives in soil and dust in parts of the U.S. and the world.
  • People with certain health conditions or demographic factors are at higher risk for severe illness.
An illustration of a group of sick people


Valley fever is a lung infection caused by breathing in spores from Coccidioides.

Coccidioides lives in the soil and dust in certain areas of the United States and the world. Activities that disturb soil and dust (like windstorms and construction) increase risk of breathing in spores.

Cats and dogs can also get Valley fever. Valley fever does not spread between people or between people and animals.

Uncommon sources of Valley fever

In extremely rare cases, people can get the infection from other sources, such as:

  • An organ transplant if the organ donor had Valley fever
  • Inhaling spores from a wound infected with Coccidioides
  • Contact with contaminated objects (such as rocks or shoes)

Most people who get Valley fever never get it again. Relapses are very rare.

Biology of Coccidioidomycosis

Print version

Image of the life cycle of Coccidioidescapsulatumcapsulatum: Environmental Form, Host-associated Form, and Areas of Endemicity for Coccidioidomycosis
Inhaled mold spores from Coccidioides turn into yeast in the lungs.

In the environment, Coccidioides ssp. exists as a mold (1) with septate hyphae. The hyphae fragment into arthroconidia (2), which measure only 2-4 µm in diameter and are easily aerosolized when disturbed (3). Arthroconidia are inhaled by a susceptible host (4) and settle into the lungs. The new environment signals a morphologic change, and the arthroconidia become spherules (5). Spherules divide internally until they are filled with endospores (6). When a spherule ruptures (7) the endospores are released and disseminate within surrounding tissue. Endospores are then able to develop into new spherules (6) and repeat the cycle.

Who is at risk

Risk of severe disease

Most of the time people do not get sick from breathing in Coccidioides spores. When people get sick, the majority get better on their own.

Certain groups of people may be at higher risk for developing the severe forms of Valley fever, such as:

  • People who have weakened immune systems, for example, people who:
    • Have HIV/AIDS
    • Have had an organ transplant
    • Are taking medications such as corticosteroids or TNF-inhibitors
  • Pregnant women
  • People who have diabetes
  • People who are Black or Filipino
  • People over 60 years of age


Scientists are continuing to work on a vaccine to prevent Valley fever with minimal side effects. No vaccines are available at this time.

It’s very difficult to avoid breathing in the fungus Coccidioides in areas where it lives in the environment.

There are still some ways to help reduce exposure to Coccidioides and risk for infection. Some steps to take include:

  • Avoid areas with a lot of dust like construction or excavation sites.
  • Stay inside during dust storms and close your windows.
  • Avoid activities involving contact with soil like gardening.
  • Use air filtration measures indoors.
  • Clean skin injuries well with soap and water to prevent infection.

Healthcare providers may prescribe antifungal medications to people at increased risk to prevent infection.

A construction site with dust flying.
Avoid areas around construction to help reduce exposure to the fungus.

Workplace risk and prevention

Workers who are concerned about Valley fever should contact their occupational health or risk management department. If a workplace does not have these services, employees should contact their local health depatment.

There is no evidence showing that antifungal medication prevents infection after a workplace exposure to Coccidioides. People who are exposed to the fungus and develop symptoms of Valley fever, should contact.

Resources for workplaces: