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Public Health

Vetted resources and information on current public health events.

What is Valley Fever?

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”).

The fungus is known to live in the soil in the southwestern United States and parts of Mexico and Central and South America. The fungus was also recently found in south-central Washington. People can get Valley fever by breathing in the microscopic fungal spores from the air in these areas.

Most people who breathe in the spores don’t get sick, but some people do. Usually, people who get sick with Valley fever will get better on their own within weeks to months, but some people will need antifungal medication. Certain groups of people are at higher risk for developing the severe forms of the infection, and these people typically need antifungal treatment. It’s difficult to prevent exposure to Coccidioides in areas where it’s common in the environment, but people who are at higher risk for severe Valley fever should try to avoid breathing in large amounts of dust if they’re in these areas.

Valley Fever Infection

Many people who are exposed to the fungus Coccidioides never have symptoms. Other people may have symptoms that go away on their own after weeks to months. If your symptoms last for more than a week, contact your healthcare provider.

Symptoms of Valley fever include:
  • Fatigue (tiredness)
  • Cough
  • Fever
  • Shortness of breath
  • Headache
  • Night sweats
  • Muscle aches or joint pain
  • Rash on upper body or legs

In extremely rare cases, the fungal spores can enter the skin through a cut, wound, or splinter and cause a skin infection.

Incubation and Disease Course

Symptoms of Valley fever may appear between 1 and 3 weeks after a person breathes in the fungal spores. The symptoms of Valley fever usually last for a few weeks to a few months. However, some patients have symptoms that last longer than this, especially if the infection becomes severe.

Severe Valley Fever

Approximately 5 to 10% of people who get Valley fever will develop serious or long-term problems in their lungs. In an even smaller percent of people (about 1%), the infection spreads from the lungs to other parts of the body, such as the central nervous system (brain and spinal cord), skin, or bones and joints.

Cimate Change & Valley Fever

The fungus is endemic to the hot, dry soils of the Southwest; 97% of all U.S. cases of Valley fever are reported in Arizona and California, according to the California Department of Public Health. But that could change: Fungal infections, including Valley fever, are increasingly being diagnosed outside of their usual ranges.

One study in the journal GeoHealth projected that, due to climate change, the range of Valley fever could spread east, through the Great Plains and north, to the Canadian border, before the end of the century. 

“As the temperatures warm up, and the western half of the U.S. stays quite dry, our desert-like soils will kind of expand and these drier conditions could allow coccidioides to live in new places,” said Morgan Gorris, who led the GeoHealth study while at the University of California, Irvine, and is now a staff scientist at the Los Alamos National Laboratory.

Around 20,000 cases of Valley fever were reported in 2019, but the Centers for Disease Control and Prevention says this is likely an underestimate. While easily diagnosed with a blood test, Valley fever has long been misdiagnosed or underdiagnosed due to lack of knowledge about the disease by both the public and physicians.

“I think fungi are really the coming superbugs. I think they’re really the ones that are going to be problematic over the next decade. And Valley fever is going to be a key part of that,” said Thompson of UC Davis. “They are really here to stay. This battle is sort of just beginning.”