What is Valley fever?
Valley fever is a disease that usually affects the lungs. It is caused by breathing in fungal spores that live in soil. Its medical name is coccidioidomycosis (pronounced like kok-SID-ee-oy-doh-my-KOH-sis), but most people simply call it Valley fever.
The disease was first identified in California’s San Joaquin Valley, which is how it got its name. Surprisingly, only about half of people who get Valley fever actually have a fever.
The illness is caused by Coccidioides, a fungus found in soils in parts of North America’s Southwest desert, especially Arizona and California. When soil is disturbed by wind, construction, farming or any earth-disrupting activities, tiny spores from the fungus can become airborne.
People and animals can then breathe in those spores without even realizing it and develop a lung infection. In about 1 out of 100 cases, the disease can spread outside of the lungs into the bones, skin or brain and cause much more severe disease.
Valley fever history and timeline
Learn about where the fungus causing Valley fever lives, how it spreads, how it’s monitored in the environment, its pathology and its public health implications.
Roughly 20,000 cases of Valley fever are reported each year in the United States, which typically represent the sickest patients. Of those cases, 20–40% require hospitalization and an estimated 200 deaths occur, although Valley fever-related deaths are undercounted.
Not only is infection most common in the Southwest United States, but cases are higher in Arizona than any other state, specifically in Maricopa, Pima and Pinal counties. In Arizona, cases each year have ranged between 5,000 and almost 12,000 over the last decade.
Millions of people in the United States live in an area where Valley fever fungus is present in soil, and the vast majority of them live right here in Phoenix and Tucson (southern Arizona). The fungus thrives in Arizona’s hot, arid and low-humidity climate, and each year infections are most common in October through December in the state.
Millions of people in the United States live in an area where Valley fever fungus is present in soil, and the vast majority of them live right here in Phoenix and Tucson (southern Arizona). The fungus thrives in Arizona’s hot, arid and low-humidity climate, and each year infections are most common in October through December in the state.
Symptoms and health impacts
Nearly all mammals can become infected with the spores that cause Valley fever if they are exposed. If you don’t have a friend, neighbor or family member who has had Valley fever, you probably know someone whose dog got it after digging in soil!
Valley fever symptoms can vary widely from person to person. Some people may only feel a little more tired than usual and never think to see a doctor, which means many cases go unreported. Others feel quite sick; with fatigue, a cough, fever, headache, shortness of breath, night sweats, and muscle and joint pain and are often mistakenly diagnosed with the flu or pneumonia before Valley fever is even considered, sometimes weeks later.
In a smaller number of cases, the infection becomes more serious and can cause lasting lung problems or, in rare cases, spread to other parts of the body like the skin, bones, joints or brain.
Valley fever’s impact goes beyond the patient; it extends to families, employers and the entire healthcare system. The numbers below are averaged from a study of Arizona Valley fever patients, and they show what might be closer to the actual costs of Valley fever infections.
$87,000
Hospital visit charges, *adjusted for inflation
202 days
Symptom duration
96 days
Unable to do daily activities
31 days
Missed work
17 days
Missed school
Diagnosis and treatment
Learning about Valley fever might be the most important step you take today.
The same study mentioned above showed that patients who know about Valley fever before they see a doctor are more likely to ask for a Valley fever test and more likely to actually get diagnosed. So just by reading this, you are already ahead.
If you have had a cough and fatigue lasting more than a week, tell your doctor and ask specifically about Valley fever testing. You may need to advocate for yourself, as Valley fever can look like the flu or pneumonia and providers don’t always think about Valley fever right away.
For more on how Valley fever is diagnosed and treated, see the IDSA clinical guidelines.
If you’re looking for a provider who specializes in Valley fever, the Valley Fever Center for Excellence is a great resource.
Mythbusters
Think you know Valley fever? Maybe think again. Valley fever is one of the most misunderstood diseases in the Southwest, and misunderstandings can delay diagnosis by weeks or even months. Test your knowledge by flipping each card to debunk the common myths about Valley fever.
Ask, answer, act
Got a question? We’ve got a quick answer and the right place to go.
Answer: The only way to know for sure is to test. There are specific tests for Valley fever, flu and COVID-19. These illnesses share many symptoms, so if your cough, fatigue or shortness of breath has lasted at least a week, ask your doctor to test you for Valley fever in addition to other illnesses. A rash along with respiratory symptoms makes Valley fever more likely than the alternatives.
Act: If your provider needs help ordering tests for Valley fever, contact the Valley Fever Center for Excellence.
Answer: Higher-risk activities include hiking or driving ATVs in dusty outdoor areas, gardening that breaks soil for the first time and construction or renovation involving ground disturbance. Digging in already-planted soil is lower risk. Valley fever spores are widespread throughout southern Arizona, so any activity that exposes you to dust can expose you to Valley fever. Dust storms (haboobs) have not been linked to a measurable spike in Valley fever cases. The fungus that causes Valley fever does not grow in higher elevation like in northern Arizona.
Act: Visitors to the Tucson area can find local health guidance at Pima County’s Visitor Health page. Learn more about exposure risks at valleyfeverarizona.org.
Answer: Wet the ground before digging and minimize unnecessary soil disturbance. During dusty outdoor tasks like gardening, yard work, construction or home renovation, consider wearing an N95 respirator mask, especially if yo have a weakened immune system or other risk factors.
Act: Find practical guidance for residents and high-risk workers at valleyfeverarizona.org or the Valley Fever Center for Excellence.
Answer: Yes. Underlying lung disease, some heart conditions and diabetes are linked to more severe Valley fever. Anyone with a suppressed immune system due to cancer, chemotherapy, steroids or other immunosuppressive medications faces significantly higher risk. Pregnant women are also at elevated risk, particularly during the third trimester and immediately after delivery and should avoid outdoor dust exposure during that time.
Act: Talk to your doctor about your personal risk level. The IDSA clinical guidelines outline who may need closer monitoring or additional precaustions.
Answer: If your cough or fatigue has lasted more than a week, see your doctor and ask specifically for a Valley fever test. Studies show patients who ask are more likely to get diagnosed. Don’t wait if you have trouble breathing, a fever that doesn’t go away or if you can’t keep fluids down. Those are signs you should seek care right away.
Act: Find a Valley fever specialist through the Valley Fever Center for Excellence. Call 911 or go to the ER for severe or emergency symptoms.
Answer: Arizona has strong resources for both patients and providers, from clinical guidelines to specialist referrals.
Act: Visit valleyfeverarizona.org for ADHS prevention and awareness resources, the Valley Fever Center for Excellence for specialist referrals and the IDSA guidelines for diagnosis and treatment guidance for healthcare providers.
Answer: Arizona public health tracks Valley fever cases year-round and alerts the public and healthcare providers when cases are rising. Public health departments, universities and clinicians are working together to identify who’s most at risk, improve prevention and help providers diagnose Valley fever earlier and more accurately.
Act: See the latest case counts and trends on the ADHS Valley fever data dashboard and annual reports.