An Overview of Valley Fever

Also known as coccidioidomycosis

Valley fever—also known as coccidioidomycosis—is an infection caused by exposure to the coccidioides fungus or mold, which is commonly found in the desert of the southwestern United States. Though not contagious, valley fever can cause symptoms like cough, fever, rashes, and tiredness just a few weeks after inhaling the fungus spores.

Cases of valley fever usually resolve on their own, but in more severe cases, healthcare providers will treat the infection with antifungal medications.

A wall of dust blows across the desert near Phoenix, Arizona.

 John Sirlin / EyeEm / Getty Images

Can Animals Get Valley Fever?

Humans aren’t the only species to come down with valley fever. Most mammals are capable of coming down with valley fever, dogs being the most common. However, valley fever has been identified in sea otters and dolphins as well.

What Is Valley Fever?

Valley fever is a disease caused by a fungus smaller than a speck of dust. This fungus is so tiny and lightweight, the slightest change in air movement can launch it into the air.

While valley fever is relatively rare in the United States as a whole, in the southwestern United States, it’s about as common as one in every 957 people. This means if you live in or travel through the southwestern United States, the chance of coming across coccidioides is high.

What Is the Medical Term for Valley Fever?

Coccidioidomycosis, or cocci for short, is the medical way to say “valley fever”—a common lung infection caused by the coccidioides fungus living in the soil in the desert southwest.

Since valley fever is from a fungus, it is not considered contagious. This fungus lives within the top 12 inches of dirt, making it easy to spread during dust storms, construction, and while driving down dirt roads.

Every year, Arizona experiences as many as 175 dust storms, which is one reason they may have the highest diagnosis rates for valley fever in the United States.

This condition affects more than just humans. It also affects the pets living in these regions—especially animals who spend most of their time outdoors or who frequently have their nose to the ground sniffing the dirt.

Where Is Valley Fever Found?

The fungus responsible for valley fever thrives in dry, desert soil, making it particularly common in:

  • Arizona
  • Southwest New Mexico
  • El Paso, Texas
  • Southern California
  • Eastern Washington

This fungus is also sometimes found in parts of Mexico, Central America, and South America.

Most Common Locations for Valley Fever

Here is a snapshot of where valley fever typically takes place:

  • Sixty percent of all valley fever infections will occur within Maricopa, Pinal, and Pima counties in Arizona.
  • Thirty percent of all value fever infections occur in Kern, San Luis Obispo, and Tulare counties in California.
  • Ten percent of all valley fever infections are found throughout southwestern United States, Washington, Mexico, and Central and South America.

Symptoms

While about 60% of people who contract valley fever will have no symptoms, the remaining 40% will show symptoms.

From the time you breathe in the fungal spore, it will take one to three weeks for symptoms to appear. These symptoms can last anywhere from a few weeks to several months.

In rare cases, the symptoms can last longer than a year. Surprisingly, more than one-third of all pneumonia cases in Arizona come from valley fever.

Common Symptoms

Valley fever often shows up with flu-like symptoms, including:

  • Fatigue
  • Cough
  • Fever
  • Shortness of breath
  • Chest pain
  • Headache
  • Night sweats
  • Muscle aches
  • Joint pain
  • Rash on legs or torso

In severe cases, valley fever will spread from the lungs to other organs like the brain, skin, and bones.

Risk Factors and Complications

While valley fever is possible for anyone who breathes in the right dust spore, those with the highest risk are:

  • Anyone more than 60 years old
  • Pregnant women in their third trimester
  • Construction workers
  • Agricultural workers
  • Military members doing fieldwork or training
  • African Americans and Asians
  • People with weakened immune systems

Complications

While many people will recover from valley fever, others will develop more severe conditions. In about 1% of those with valley fever, the infection will spread outside the lungs infecting the:

  • Skin
  • Bones
  • Liver
  • Heart
  • Brain

The most deadly form of valley fever occurs when the infection reaches the brain. When this happens, valley fever becomes a form of meningitis. Those with meningitis from valley fever will need to take antifungal medications like fluconazole for the rest of their life. 

Prevention and Treatment

Since valley fever exists anywhere there is dust, complete avoidance is impossible. However, there are ways to lower your overall risk of contracting valley fever. This includes:

  • Staying indoors during a dust storm
  • Staying inside if something is going on that is stirring up the dirt, like landscaping or construction
  • Wearing a face mask—especially in the summer when sudden dust storms are most common

Before receiving treatment for valley fever, you will need a blood test to confirm the presence of the fungus in your body. After being diagnosed, you will likely receive a prescription for an antifungal medication such as fluconazole. Most people will be on an antifungal medication for about three to four months, although others may need medication longer than this.

It’s important for those diagnosed with valley fever to be monitored for at least a year after diagnosis. Follow-up appointments often include lab tests or X-rays.

A Word From Verywell

Valley fever can range from mild to severe. If you think you or your pet may have valley fever and it feels like you’re not getting any better, take time to make an appointment with a healthcare provider.

While some people can get valley fever and never know it, others aren’t so lucky. If after a week you’re not getting better, or if you only seem to be getting worse, it’s time to speak to your healthcare provider. 

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Article Sources
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  1. Centers for Disease Control and Prevention. Valley fever awareness. Updated December 18, 2020.

  2. Weather.gov. Radar-based characteristics of dust storms in Arizona.

  3. Centers for Disease Control and Prevention. Valley fever (coccidioidomycosis) statistics. Updated July 22, 2020.

  4. MedlinePlus. Valley fever. Updated September 23, 2016.