Valley Fever Explained: Symptoms, Causes, Treatment, and Who Is at Risk

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026

TL;DR

Valley fever is a fungal lung infection caused by breathing in spores from Coccidioides fungi that live in the soil of parts of the U.S. Southwest, Mexico, and Central and South America. It often causes flu-like symptoms that begin one to three weeks after exposure and can take months to fully resolve. Most cases clear up on their own without treatment, but people over 60, those with weakened immune systems, pregnant people, and individuals with certain health conditions face a higher risk of serious illness and should seek care promptly. There is no vaccine, so avoiding dust exposure is the main prevention.

Quick Answer

• What is valley fever? A fungal lung infection caused by breathing in Coccidioides spores from soil in parts of Arizona, California, Nevada, Utah, New Mexico, Texas, and Washington.

• How does it spread? Disturbed soil — from wind, farming, construction, or dust storms — releases spores into the air, and people breathe them into their lungs.

• What are the symptoms? Fever, cough, tiredness, shortness of breath, chest pain, night sweats, headache, joint pain, and sometimes a rash, usually starting 1 to 3 weeks after exposure.

• Do you need treatment? Most cases clear on their own; antifungal medicines are used when symptoms persist, worsen, or the person is at higher risk of complications.

• Can you get it again? For most people, one infection provides immunity; those with weakened immune systems can be reinfected.

What Is Valley Fever?

Valley fever is a fungal infection caused by organisms in the Coccidioides genus (pronounced kok-sid-e-OI-deze). It is sometimes called San Joaquin Valley fever or, by its medical name, acute coccidioidomycosis (kok-sid-e-oi-doh-my-KOH-sis).

Two fungus species cause it: Coccidioides immitis and Coccidioides posadasii. Both live in the soil of specific regions. When anything disturbs that soil — farming, construction, wind, or a dust storm — the fungi's microscopic spores fly into the air.

People then breathe those spores into their lungs. Inside the body, the spores grow into the fungus's main form and can cause infection. The illness may be mild and get better without treatment, but more serious cases need antifungal medicines.

How Do You Know If You Have Valley Fever?

Symptoms depend on the form of the infection. The first and most common stage is the acute form — valley fever itself. If it does not clear, it can become chronic, an ongoing lung infection. In its rarest and most serious form, the fungus disseminates, spreading beyond the lungs to other parts of the body.

Acute Valley Fever Symptoms

The acute form often causes few or no symptoms at all. When symptoms do appear, they typically start one to three weeks after contact with the fungus.

The symptoms tend to feel like the flu and can range from minor to serious:

Symptom	What You May Notice
Fever	Elevated body temperature
Cough	Often persistent
Tiredness	Fatigue that can outlast other symptoms
Shortness of breath	Trouble catching your breath
Chest pain	Especially when breathing in
Night sweats	Sweating during sleep
Headache	Frequent or persistent
Joint pain	Mainly in the ankles, knees, and wrists
Rash	On the skin

On a chest X-ray, acute valley fever often looks like pneumonia. For people who develop symptoms, especially serious ones, the illness course varies from person to person. Full recovery can take months, and tiredness and joint aches can last even longer.

Chronic Valley Fever

If the first infection does not fully clear, it can move into an ongoing form of pneumonia. This complication is most common in people with weakened immune systems. Symptoms include a low-grade fever, weight loss, a cough that may bring up blood-tinged mucus, chest pain, and areas of infection in the lungs called nodules, cavities, or scarring.

Disseminated Valley Fever

The disseminated form is the most serious but is not common. The infection spreads from the lungs to other parts of the body — mainly the skin, bones, liver, brain, heart, and the meninges (the membranes that protect the brain and spinal cord).

Symptoms depend on which body parts are affected:

Body Area	Possible Symptoms
Skin	Nodules and sores that are more serious than the rash seen with the acute form
Bones	Painful sores in the spine, legs, knees, or other bones
Joints	Painful, swollen joints, mainly in the knees or ankles
Brain and spinal cord	Meningitis, an infection of the membranes and fluid around the brain and spinal cord

When Should You See a Doctor?

Seek medical care if you have valley fever symptoms and you are older than 60, have a weakened immune system, are pregnant, or are of Filipino or African heritage.

Care is most important if you live in or have recently traveled to an area where the illness is common, or if your symptoms are not getting better. Be sure to tell your healthcare professional if you have traveled somewhere where valley fever is common — travel history is one of the key clues to the diagnosis.

What Causes Valley Fever?

Breathing in spores of two fungi — Coccidioides immitis and Coccidioides posadasii — causes valley fever. These fungi live in the soil in parts of Arizona, California, Nevada, Utah, New Mexico, Texas, and Washington. They are also found in northern Mexico and Central and South America.

The wind carries the tiny spores. Once inside the lungs, the spores grow and turn into the main form of the fungus in the body.

Who Is at Higher Risk?

Anyone who breathes in the spores is at risk of infection. But certain factors raise the odds, or raise the odds of a more serious illness.

Risk Factor	Why It Matters
Being in an endemic area	Anyone who breathes the spores is at risk. Living in an endemic area and spending time outdoors raises the risk further.
Dusty outdoor jobs	Construction, road and farm work, ranching, archaeology, and military training expose people to dust where the fungus is common.
Being of certain races	People whose families are from the Philippines and Africa are more likely to get serious infections, though experts do not know why.
Pregnancy	Pregnant people are more likely to get serious infections when infected during the third trimester or right after their babies are born.
Weakened immune system	Includes people living with AIDS, those treated with steroids or anti-rejection medicines, and people taking immune-suppressing medicines for autoimmune conditions such as rheumatoid arthritis and Crohn's disease.
Diabetes	May raise the risk of certain lung infections.
Older age	Older adults are more likely to get valley fever, possibly because immune systems weaken with age or because of other medical conditions.

What Are the Complications?

Most people who get valley fever pneumonia recover without complications. But serious complications can occur.

Serious pneumonia is possible. People whose families are from the Philippines or Africa, and those with weakened immune systems, may get very ill.

Burst lung cavities happen in a small percentage of people. They develop thin-walled nodules, also called cavities, in their lungs. Many nodules and cavities go away without causing any issues, but some cavities may burst, causing chest pain and trouble breathing. Treatment for a burst lung nodule might involve putting a tube into the space around the lungs to remove the air, or surgery to fix the damage.

Disseminated disease is the most serious complication, though it is not common. If the fungus spreads through the body, it can cause skin sores, joint pain, swelling and inflammation, and meningitis — an infection of the membranes and fluid covering the brain and spinal cord. Meningitis may be fatal if not treated.

How Is Valley Fever Diagnosed?

To diagnose valley fever, your healthcare professional looks at your medical history and your symptoms. It is hard to diagnose based on symptoms alone, because symptoms are often mild and resemble other illnesses. Even on a chest X-ray, valley fever can look much like other lung infections such as pneumonia.

To pin down the diagnosis, healthcare professionals may order one or more of the following tests:

Test	What It Checks
Sputum smear or culture	A sample of the matter that comes up while coughing (sputum) is checked for coccidioides organisms.
Blood tests	A blood test can show antibodies against the fungus that causes valley fever.
Imaging tests	A CT scan, MRI, or chest X-ray looks for valley fever pneumonia.
Lung biopsy	A healthcare professional takes a sample of lung tissue for study under a microscope.
Skin test	May show that you have had valley fever in the past and cannot get it again (immunity).

How Is Valley Fever Treated?

Valley fever most often clears up on its own. Some people need medicines.

Antifungal Medicines

A healthcare professional may prescribe an antifungal medicine when symptoms do not improve, last a long time, or get worse. These medicines are also used if you are at higher risk of complications, or if the infection is chronic or disseminated.

The antifungal fluconazole (Diflucan) most often treats all but the most serious forms of the disease. Another option is itraconazole (Sporanox, Tolsura).

Antifungal medicines can have serious side effects, though these tend to go away once you stop taking the medicine. Side effects of fluconazole and itraconazole may include upset stomach, vomiting, and loose stools. Fluconazole may also cause hair loss, dry skin, dry mouth, and chapped lips.

For more serious infections, an antifungal medicine most often given as a pill may be used. These include amphotericin B (Abelcet, Ambisome), voriconazole (Vfend), posaconazole (Noxafil), and isavuconazonium (Cresemba).

Monitoring After the Infection

For many people, having valley fever once means they cannot get it again. But for people with weakened immune systems, the infection may come back. Even if you do not have treatment, your healthcare professional may watch you for complications or relapse for at least a year.

How Can You Prevent Valley Fever?

There is no vaccine to prevent valley fever.

If you live in or visit areas where it is common, take steps to prevent infection. The dry season following a rainy season is when the chance of infection is highest.

Prevention Step	What to Do
Wear a mask	Cover your mouth and nose in dusty conditions.
Avoid very dusty areas	Stay clear of construction sites and similar locations.
Stay inside during dust storms	Limit outdoor exposure when dust is in the air.
Wet soil before digging	Dampen the ground first; stay away from soil altogether if you are at higher risk.
Close doors and windows	Keep them tightly closed in dusty areas.
Clean skin injuries	Wash cuts with soap and water.

Preparing for Your Appointment

See your healthcare professional if you get symptoms of valley fever and are in or have just come back from an area where this condition is common.

Make a list of the following before your visit:

• Your symptoms, and when they began.

• When you have traveled recently, and where.

• Key medical information, including other conditions you have and any medicines, vitamins, or supplements you take, including doses.

• Questions to ask your healthcare professional.

Questions to ask might include:

• What is the most likely cause of my symptoms?

• What tests do I need?

• What treatment do you suggest, if any?

• I have these other health conditions — how can I manage these together?

• Am I at risk of long-term complications from this condition?

Your healthcare professional may ask you:

• Have your symptoms gotten worse over time?

• Does your work or what you do for fun involve spending time in dusty outdoor places?

• Are you pregnant?

Conclusion

Valley fever is a fungal lung infection that hides behind flu-like symptoms and often goes unrecognized — even on a chest X-ray, it can look like pneumonia. The good news: most cases clear up on their own, and one infection usually provides lasting immunity for most people.

Your next steps: if you have flu-like symptoms and recently spent time in the U.S. Southwest, Mexico, or Central or South America — especially after working outdoors in dust or during a dry spell — tell your healthcare professional about your travel. Before your visit, write down when your symptoms began, where you have traveled, and a full list of your medicines and conditions. If you live or work in a high-risk area, use dust precautions: wear a mask, stay inside during dust storms, and wet the soil before digging. If you are over 60, pregnant, have a weakened immune system, or are of Filipino or African heritage, do not wait — seek care early.

Frequently Asked Questions

What is valley fever and how do you get it?

Valley fever is a fungal lung infection caused by breathing in spores from Coccidioides immitis and Coccidioides posadasii, fungi that live in the soil of parts of Arizona, California, Nevada, Utah, New Mexico, Texas, and Washington, as well as northern Mexico and Central and South America. Anything that disturbs the soil — wind, farming, construction — releases spores into the air, and people breathe them into their lungs.

What does valley fever feel like?

Symptoms are flu-like and often begin one to three weeks after exposure: fever, cough, tiredness, shortness of breath, chest pain when breathing in, night sweats, headache, joint pain (mainly in the ankles, knees, and wrists), and sometimes a rash. Full recovery can take months, and tiredness and joint aches can last even longer.

Does valley fever go away on its own?

In most cases, yes. Valley fever most often clears up on its own without treatment. Antifungal medicines are reserved for symptoms that do not improve, last a long time, or worsen, or for people at higher risk of complications and those with chronic or disseminated infection.

How long does valley fever last?

The course varies from person to person. It can take months to fully recover, and tiredness and joint aches can persist even longer than the other symptoms.

Who is most at risk for serious valley fever?

People older than 60, those with weakened immune systems (including people living with AIDS or taking steroids, anti-rejection medicines, or medicines for autoimmune conditions such as rheumatoid arthritis and Crohn's disease), pregnant people (especially if infected in the third trimester or right after birth), people with diabetes, and people whose families are from the Philippines or Africa are at higher risk of serious infection.

Can you get valley fever more than once?

For many people, having valley fever once means they cannot get it again — a skin test can even confirm this immunity. However, for people with weakened immune systems, the infection may come back.

Is there a vaccine for valley fever?

No. There is currently no vaccine to prevent valley fever. Prevention relies on dust precautions: wearing a mask, avoiding very dusty areas, staying inside during dust storms, wetting soil before digging, keeping doors and windows closed, and cleaning skin injuries with soap and water.

How is valley fever diagnosed?

Because symptoms resemble other illnesses and a chest X-ray can look like pneumonia, diagnosis relies on your medical history plus tests: a sputum smear or culture, a blood test for antibodies against the fungus, imaging tests (CT, MRI, or chest X-ray), a lung biopsy, or a skin test that can show past infection and immunity.

What medicines treat valley fever?

Fluconazole (Diflucan) most often treats all but the most serious forms, with itraconazole (Sporanox, Tolsura) as another option. More serious infections may be treated with amphotericin B, voriconazole, posaconazole, or isavuconazonium. Side effects such as upset stomach, vomiting, and loose stools can occur but tend to resolve after stopping the medicine.

References

[1] Valley fever — Symptoms & causes — Mayo Clinic, reviewed Dec. 24, 2025.

[2] Valley fever — Diagnosis & treatment — Mayo Clinic, reviewed Dec. 24, 2025.

Health information, not medical advice. This article is for general education and is not a substitute for professional diagnosis or treatment. Always consult a qualified healthcare provider about your own health, and seek emergency care for urgent symptoms.