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Valley fever may be more common than expected

A woman on a couch holds a hand to her forehead as she looks at a thermometer.

June 26, 2025—Valley fever may be up to 18 times more common in the United States than reported, according to a recent study in JAMA Network Open.

Valley Fever, or coccidioidomycosis, is a fungal lung infection caused by breathing in Coccidioides spores found in soil. Symptoms are usually similar to pneumonia, says the Centers for Disease Control and Prevention (CDC). And some people don't experience symptoms at all. But about 5% to 10% of people with the condition have serious or long-lasting lung symptoms. In rare cases, the disease can spread throughout the body and affect the brain, skin and other organs.

Unveiling a stealth infection

Each year, 10,000 to 20,000 valley fever cases are reported, according to CDC. But only 28 states and Washington, D.C., track the condition. Because the symptoms of valley fever are so similar to pneumonia and other common lung infections, it often goes undiagnosed.

That's a problem: The right diagnosis is key to getting the right antifungal treatment.

To find out how common valley fever really is, researchers built a mathematical model. They used past studies and expert opinions to estimate factors like how often people with valley fever have symptoms, go to the doctor and get the right diagnosis. Then they applied that to the 2019 data from the National Notifiable Diseases Surveillance System. They found that, in 2019:

  • 273,000 people had valley fever—about 10 to 18 times more than reported.
  • 23,000 people were hospitalized from the condition.
  • 900 people died of valley fever.

The fungus that causes valley fever is found in soil, and, in the U.S., it's most common in California and Arizona. An estimated 125,000 cases came from those states.

Another 46,000 cases came from states known to have valley fever spores but that are considered lower risk:

  • Nevada.
  • New Mexico.
  • Texas.
  • Utah.
  • Washington.

But an estimated 103,000 cases—more than a third of the total—came from the 43 states (plus Washington, D.C.) where the levels of valley fever spores are unknown. That means people may have valley fever even if they're in an area where the disease is unexpected.

Recognizing valley fever

Valley fever doesn't always cause symptoms. When it does, they usually mirror other bacterial or viral infections, like pneumonia. According to the American Lung Association (ALA), symptoms may include:

  • Fever.
  • Fatigue.
  • Cough.
  • Headache.
  • Difficulty breathing.
  • Muscle aches or joint pain.
  • Night sweats.
  • Upper body or leg rash.

In most cases, people with valley fever recover on their own, says the ALA. But if symptoms are severe or last longer than eight weeks, you may need antifungal medications.

Ask your doctor whether a blood test for valley fever might be right for you if:

  • You think you might have been exposed to the spores that cause valley fever.
  • Your pneumonia symptoms are lasting for weeks.

Concerned about your risk? Ask your doctor for advice. You can also learn more about the different types of pneumonia—and how to prevent it—in our Pneumonia health topic center.

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