What Is Valley Fever?

Medically Reviewed by Sabrina Felson, MD on May 29, 2023
8 min read

Valley fever, or coccidioidomycosis, is an infection. It's caused by a fungus called Coccidioides.

Many of us are more familiar with the fever, chills, and other signs of the flu than we’d like to be. If you live in the southwestern United States or certain other areas, there’s a small chance that these symptoms could signal valley fever.

The fungus grows in the ground. When something stirs up the soil, spores from the fungus fly into the air where people breathe them in.

Most people don’t get sick. And when valley fever symptoms do appear, they usually go away on their own. If not, there are medicines that can typically clear them up. But in rare cases, the fungus spreads to other parts of the body. That’s much more serious, so it’s important to know what’s happening.

Another reason to keep a lookout: Pets can come down with valley fever, too.

Valley fever is also known as San Joaquin Valley fever or desert rheumatism.

The types of fungus that cause valley fever thrive in dry, desert soil. When the wind picks up their spores, it can blow them for hundreds of miles. They exist in these areas of the U.S.:

  • Arizona
  • Southwestern New Mexico
  • Areas around El Paso, Texas
  • Central and Southern California, especially the San Joaquin Valley
  • Eastern Washington state

The fungus’ area also reaches down into Mexico. And it has turned up in Central and South American countries, including Argentina, Brazil, Colombia, Guatemala, Honduras, Paraguay, and Venezuela.

Valley fever in California

Valley fever cases have gone up in California from 2000 to 2018. Drought in California effects the number of new valley fever cases. This is because the valley fever fungus lives and grows in soil. Even when it's dry from drought and other organisms are killed, the fungus can live. During the actual drought, there aren't as many new valley fever cases, probably because the fungus is inactive in the soil. But when it rains again and the fungus can grow, more people get sick. Drought in California causes there to be more valley fever cases in the years following. 

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

  • Fresno​
  • Kern
  • Kings
  • Madera
  • Tulare

​The California Central Coast and Northern San Joaquin (Central) Valley regions had an increasing number of valley fever cases. The counties in this region include:

  • Monterey
  • San Luis Obispo
  • Santa Barbara
  • Ventura​
  • Merced
  • San Benito
  • San Joaquin
  • Stanislaus​​

When do most people get it?

You can get valley fever at any time of the year. But more people get diagnosed in the fall, between late September to November, compared to other months. Because it takes weeks for people to develop symptoms, this means that people who get the infection usually catch it in the summer, between June to early September.

If you go to the affected regions, you could be exposed. Someone who is age 60 or older is more likely to get it. The risk is also greater for:

  • People with weakened immune systems
  • P eople who are p regnant
  • People with diabetes
  • People of African descent and Hispanic, Native American, and Filipino people, likely due to genetic reasons

If you work, live, or travel in areas where there are high rates of valley fever, you're also at a higher risk. This is especially true if you:

  • Work in close contact with dirt or dust (such as in landscaping, construction, military work, field work, or archaeology)
  • Are around dirt or soil that is stirred up (like construction or excavation sites)

If you work or live in an area where valley fever is common, you should speak with your employer or landlord about how to prevent infection.

Six out of every 10 people who get infected with valley fever will have no symptoms. Their bodies will fight off the infection. But for others, signs of valley fever usually show up 1 to 3 weeks after the fungus gets into your lungs. You might have:

Valley fever rash

This rash can show up in different ways. Usually it's:

  • Painful or tender
  • Slightly elevated with red bumps
  • On your legs (but it can also happen on your chest, back, and arms)
  • A bluish to brown color

If symptoms do appear, recovering from them may take months. The time depends on your general health and how many of the fungus spores have gotten into your lungs.

If symptoms don’t improve on their own or you don’t get treatment, valley fever may develop into a long-term type of pneumonia. This mainly happens in people whose immune systems are weak. The symptoms include fever, unexplained weight loss, chest pains, and coughing up mucus with blood in it.

Is valley fever contagious?

Valley fever isn’t contagious, so you can’t catch it from someone else. You get the infection when you breath in fungal spores in the air. Once you breathe them in, they change form in your body tissue. You can't spread them to other people or animals once this happens.

Is valley fever serious?

Valley fever can be serious or fatal. In California, there have been over 1,000 hospitalizations each year with the infection. About 1 in 10 of these people have died in the hospital.

How long does valley fever last?

The symptoms of this this infection will usually go away on their own after a few weeks or months. A small group of people will have ongoing symptoms in their lungs. If this continues, it's called chronic pulmonary coccidioidomycosis and not valley fever anymore. With this, you may have no symptoms or have chest pains, shortness of breath, weight loss, cough up blood, of have a chronic cough. 

Disseminated valley fever

In the most serious cases, the infection moves beyond the lungs into other parts of the body. Disseminated valley fever is the most intense version, but it's uncommon. It happens when the infection moves to your skin, bones, brain, liver, heart, and the membranes that guard your spinal cord and brain.

The possible effects include skin sores that are worse than the rash mentioned above, painful, swollen joints, and meningitis, which is an infection around the brain and spinal cord

Other complications include:

  • Pneumonia
  • Air, pus, or water in the lung cavity or space outside of your lungs
  • Acute respiratory distress syndrome (ARDS)


Make the call if you have symptoms of valley fever and they last more than a week. Checking with a professional is especially important if you’re in a high-risk group.

The main test for valley fever is for your doctor to take a sample of your blood. The results should come back in a few days.

You may also be asked to cough up a mucus sample so it can be tested.

Your doctor might take an X-ray.

They might also take a sample of tissue from your body. If the tissue or blood needs to go to a lab for more tests, the results might take a few weeks to get back to your doctor.

Valley fever usually doesn’t need medical treatment. For people who are otherwise healthy, bed rest and drinking plenty of fluids are enough. Your doctor will keep a close watch on how you’re doing.

If the symptoms hang on or get worse, your doctor might prescribe a drug that attacks illnesses caused by fungus. There are several options, depending on how severe the symptoms are. In the most extreme cases, such as people who develop meningitis, lifelong medication may be necessary.


There’s no vaccine. But if you live in or visit a region where valley fever is a possibility, it helps to take commonsense precautions, such as:

  • Avoid dusty areas such as construction sites.
  • Stay indoors during dust storms, and keep the windows shut.
  • Avoid activities that put you in contact with dust and soil, such as yard work and gardening.
  • Filter the air inside your home.
  • When you drive, keep your windows closed and use recirculating air, if possible.
  • Use an N95 mask if you can't avoid dusty areas.
  • Control dust by covering dirt around your home with plants, grass, or gravel.

These steps are particularly important for people who are at high risk.

Valley fever immunity

One bit of good news: In many cases, people who have valley fever become immune for the rest of their lives.

But in rare cases, especially if you have a weakened immune system, you might get valley fever again.

Since you can’t spread it to other people, you don’t have to stay home for that reason. But it’s important to get as much rest as possible until your symptoms are gone.

Face masks

You can wear a properly fitted, National Institute for Occupational Safety and Health (NIOSH)-approved mask to protect against this infection. These include N95, N99, N100, P100, or HEPA. 

Cloth masks, KN95s, or other non-certified masks won't help as much.


You can’t spread valley fever to, or get it from, your pet. But animals can get it on their own.

Valley fever symptoms in dogs

Dogs are most vulnerable. Just like with people, many of the animals that inhale the fungus don’t get sick. When they do, they may cough, lack energy, or lose weight. If you think your pet may have valley fever, check with your vet. Other symptoms may include:

  • Pain or s​welling in their joints and limbs
  • Neck or back pain
  • Skin wounds that drain fluid
  • Lumps and bumps under their skin
  • Limping or trouble walking
  • Neurologic signs (seizures, vision changes, and loss of muscle control)
  • Swollen lymph nodes around their jaw, in front of their shoulder blades, or behind their back legs
  • Swelling, pain, cloudiness, and redness in their eyes and around the skin

Cats can also get valley fever. They might have symptoms like fever, lowered appetite, and weight loss. Breathing issues, limping, neurologic signs, and eye issues are less common in cats.

Livestock can also get the infection. But they don't show signs as often. If they do, it's usually just a cough that lasts weeks to months. 

Camels, llamas, and alpacas can get valley fever too. They usually will develop intense infection that spreads to their entire body and is fatal. Other symptoms could include weight loss, coughing, low energy, lowered appetite, limping, skin wounds, and hair loss.