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Valley fever

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  • La Fiebre del Valle en Español
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Valley Fever Basics

en Español sa Tagalog

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 exhaustion. 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. In California, on average over 1,000 people have been hospitalized with Valley fever each year, of which about 1 in 10 have died.

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 nearly 12,500 cases in 2024.

How do you get Valley fever?

People 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, goes to school, or travels in an area where the Valley fever fungus grows can breathe in these fungus spores from outdoor dust without knowing it. Not everyone who breathes in the fungus will get sick. 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 people breathe in the fungus during drier times of the year in the summer and early fall. If a person gets sick with Valley fever, it usually happens 1-3 weeks after they breathe in the fungus. This means we see more cases of Valley fever diagnosed and reported in the fall and early winter in California than at other 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. ​In fact, Valley fever gets its name from the Central (San Joaquin) Valley because that's where it is most common in California. ​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, go to school, or travel in these areas or go to other places where Valley fever has been reported, including nearby southwestern states (especially Arizona), 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.

​Top counties in California with Vall​ey fever:  

  • ​Fresno

  • Kern 

  • Kings​​​

  • ​​Madera

  • Merced

  • Monterey

  • ​San Joaquin

  • San Luis Obispo

  • Santa Barbara

  • ​Stanislaus

  • ​Tulare

  • Ventura


Valley fever is spreading and changing rapidly in California. For more information about where and when Valley fever has been reported in California, visit the CDPH Provisional Valley Fever Data Dashboard and CDPH Year-end Valley Fever Data Dashboard. ​

​Valley fever is on the rise in California

This map shows the rates (or number of cases per 100,000 people per year) of Valley fever by county in California. Rates help explain how common a disease is in an area compared to the number of people that live in that area. The darker the color on the map, the more Valley fever has been reported in that county.​​

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, the Valley fever fungus is believed to be inactive in the soil, so fewer people can breathe it in. 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.


Learn more about climate and fungal diseases


    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.


More Valley Fever Q&As

Do I have Valley fever, COVID-19, or flu?

​Valley fever, COVID-19, and flu share many of the same symptoms, including fever, cough, fatigue, and body aches. If you are experiencing these symptoms for more than 7-10 days and have been around dirt or dust outdoors in areas where Valley fever is common, contact your healthcare provider and ask about Valley fever. Laboratory tests are needed to know whether symptoms are caused by COVID-19, flu, or Valley fever. Usually, Valley fever is diagnosed using a blood test, but the lab tests for COVID-19 and flu use a respiratory sample from your nose or throat. 

Is Valley fever found only in the Central Valley?

​No. While most cases of Valley fever in California are reported in people who live in the Central Valley or Central Coast, it has been diagnosed in people living throughout California. More and more cases have also been recently reported in Central and Southern California.     

Can I get Valley fever from someone who is sick with Valley fever?

​No. Valley fever is not contagious, meaning it can't spread from one person to another. You can't get or spread Valley fever by touching or being around another person or animal that is sick with Valley fever.

Can I get Valley fever from being exposed to pesticides?

​No. Valley fever is caused by breathing in the Valley fever fungus from dust in outdoor air, not from pesticides. This fungus grows in the dirt and soil and does not come from pesticides that are sprayed on crops and farmland.       

Can my pets get Valley fever?

​Yes. Pets, including cats and dogs, can get Valley fever. Valley fever in dogs is similar to Valley fever in humans. If you're concerned about your pet's risk of getting Valley fever, or if you think your pet has Valley fever, please talk to a veterinarian. Learn more about Valley fever in pets and other animals​.

If I was born in the Central Valley, am I immune to Valley fever?

​No. Even if you've lived in California's Central Valley your whole life and have never been sick from it, you can still get Valley fever. Anyone who lives in or travels to areas where Valley fever has been reported can get Valley fever. Valley fever can affect adults and children of any age, even if they are healthy.      

 Certain groups of people are more likely to get very sick from Valley fever if they get it. Learn more about groups at risk for severe Valley fever.

If I’ve already had Valley fever, am I immune to it and can’t get sick again?

​It depends. If you've already had Valley fever, your immune system will most likely protect you from getting it again. However, in rare cases where a person's immune system is weakened because of a health condition like cancer, organ transplant, or autoimmune disease, then that person may get Valley fever again. 

How much dust do I need to breathe in to get Valley fever?

​You can get Valley fever from just one breath of dust from outdoor air that contains spores of the Valley fever fungus.

Will wearing any type of face mask help prevent Valley fever?

​Wearing a properly fitted, National Institute for Occupational Safety and Health (NIOSH)-approved respirator (mask) with particulate filters rated N95, N99, N100, P100, or HEPA may help protect you from breathing in dust and spores that can cause Valley fever. Cloth face masks, simple dust masks (with just one strap), KN95s (not certified by NIOSH), and household fabrics, such as washcloths, bandanas, and handkerchiefs, do not provide the same level of protection as N95 or higher-rated respirators. If your work involves dusty environments or soil disturbing activities, learn more about Valley fever safety in the workplace.

Learn More

  • Symptoms

  • Groups at Risk

  • Prevention Tips

Page Last Updated : August 8, 2025
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