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Valley fever

Valley Fever Basics


What is Valley fever?

Valley fever (also called coccidioidomycosis or “cocci”) is a disease caused by the Coccidioides fungus that grows in the soil and dirt in some areas of California and the southwestern United States. This fungus can infect the lungs and cause respiratory symptoms, including cough, difficulty breathing, fever, and tiredness or fatigue. In rare cases, the Valley fever fungus can spread to other parts of the body and cause severe disease – this type of Valley fever is less common and is called disseminated Valley fever.

Valley fever can be serious and even fatal. Recently in California, there have been more than 1,000 people hospitalized with Valley fever each year, of which about 1 in 10 have died in the hospital.

Did you know?

In California, the number of reported Valley fever cases has greatly increased in recent years. Since 2000, the number of cases has increased from less than 1,000 cases to more than 9,000 cases in 2019.

How do you get Valley fever?

You can get Valley fever by breathing in dust from outdoor air that contains spores of the Coccidioides fungus that grows in the soil. Like seeds from a plant, a fungus grows and spreads from tiny spores that are too small to see. When soil or dirt is stirred up by strong winds or while digging, dust containing these fungus spores can get into the air. Anyone who lives, works, or travels in an area where the Valley fever fungus grows can breathe in these fungus spores from outdoor dust without knowing it and become infected. Valley fever is not contagious, meaning it cannot spread from one person or animal to another.

Animals, including pets, can also get Valley fever.

Animals, including pets, can also get Valley fever by breathing in fungus spores from dirt and outdoor dust.


When can you get Valley fever?

In California, people can get Valley fever at any time of the year, but more cases are diagnosed and reported in the fall (late September through November) than at other times of the year. Since it often takes weeks for people who have Valley fever to develop symptoms or get properly diagnosed, this means people who get Valley fever are usually infected in the summer (June through early September), during drier times of the year.  More people also get Valley fever in the years after a drought has ended in California. Learn more about how drought impacts Valley fever. ​

Where can you get Valley ​​​​fev​er?

Most cases of Valley fever in California are reported from the Central Valley and Central Coast regions of the state. But the number of cases has also been increasing n​earby in the northern Central Valley and southern coastal areas of California. People are more likely to get Valley fever if they live, work, or travel in these areas or travel to other places where Valley fever has been reported, including nearby southwestern states, Mexico, and Central and South America. There is no commercial test available to see if the Valley fever fungus is in the dirt or dust in certain areas, but we do know that Valley fever has been diagnosed in people living throughout California. The map below shows the rates (or number of cases per 100,000 people) of reported Valley fever cases by county in California from 2014 to 2018.

From 20​00-2018: 

​​​The California Southern San Joaquin (Central) Valley region had the highest rates of Valley fever. Counties in this region include: ​

​The California Central Coast and Northern San Joaquin (Central) Valley regions had increasing rates of Valley fever. Counties in these regions include: ​

        • Fresno​
        • Kern
        • Kings
        • Madera
        • Tulare
      • Monterey
      • San Luis Obispo
      • Santa Barbara
      • Ventura​
      • Merced
      • San Benito
      • San Joaquin
      • Stanislaus​​

Valley fever is on the rise in California


What does Valley fever have to do with drought in California?


We’re learning that drought impacts the number of new Valley fever cases in California because drought affects how the Valley fever fungus lives and grows in the soil. During dry conditions and drought, the Valley fever fungus can survive in the soil, even when other microbes and organisms are killed off by lack of water. During a drought, fewer people get infected by the Valley fever fungus because the fungus is believed to be inactive in the soil. But when rain returns after a drought, the Valley fever fungus can grow again, spreading spores in dirt and outdoor dust that people can breathe in, making them sick. Overall, drought increases the number of Valley fever cases in California in the years following a drought and may allow for the Valley fever fungus to grow in the soil in more areas of California. More droughts in California may lead to an increase in Valley fever in more areas of the state.

What is a drought?

It’s a period of time when an area gets less rainfall than expected, and when temperatures are higher or hotter than normal.


    The switch between dry conditions during a drought and rainy winters following a drought creates the right conditions for the Valley fever fungus to thrive. Historically, cases of Valley fever in California have been lowest during years of drought and highest during years immediately after a drought.


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