What Is Valley Fever? Symptoms, Causes, Treatments

If you grew up in the Southwest — or you’re obsessed with the HBO series “The Last of Us” — you may already be familiar with the dangers of fungal infections, particularly Valley fever. And if you’re a pet parent, you know dogs are particularly vulnerable to this desert illness.

Valley fever used to be referred to as “desert rheumatism” because of its correlation to the desert climate and its impact on the lungs, according to the University of Arizona. The fungus that causes the respiratory illness is found in hot, dry environments. “In general, different fungal species have different environmental conditions that allow them to flourish,” says Amesh A. Adalja, MD, FIDSA, FACP, FACEP, senior scholar at Johns Hopkins Center for Health Security. As environmental conditions change, more areas may become hospitable to their growth.

The Centers for Disease Control and Prevention reported roughly 20,000 cases of Valley fever in 2019, with the caveat that this number is likely underreported by tens of thousands due to misdiagnosis. And cases are spiking again in 2024 as the state of Arizona has reported a 45 percent jump in infections from this time last year.

Thankfully, researchers are getting close to an approved preventative canine vaccine, and a vaccine for humans is also in the works (more on that later!). But until then, staying informed about Valley fever could help keep you, your family, and your pet safe. PS spoke with health experts to break down everything you need to know about Valley fever, including symptoms to watch for in dogs and humans and how to treat an exposure to the sometimes-deadly fungal spores.

Experts Featured in This Article:

Amesh A. Adalja, MD, FIDSA, FACP, FACEP, is a senior scholar at Johns Hopkins Center for Health Security.

George Thompson, MD, is a professor of clinical medicine at the University of California.

John Landry, BS, RRT, is a registered respiratory therapist and CEO of Respiratory Therapy Zone.

Oladele Ogunseitan, PhD, MPH, is the University of California presidential chair and professor of population health and disease prevention.

What Is Valley Fever?

Valley fever is a lung disease commonly found in the Southwest (Arizona, Southern California, West Texas, Nevada and Utah) because it thrives in areas with low rainfall, high summer temperatures, and moderate winter weather. It’s also known as coccidioidomycosis or cocci because it’s caused by the fungus Coccidioid that grows in soil. The respiratory illness can be deadly, especially for the immunocompromised and domestic animals. Take steps to prevent fungal infections, such as wearing protective clothing when working in areas with a high risk of exposure and being mindful of the symptoms.

“Valley fever isn’t particularly dangerous to someone with an intact immune system,” Dr. Adalja explains. “However, in the immunocompromised, Valley fever can be very dangerous and can disseminate throughout the body and cause very severe infection.” Not to mention, long COVID and certain treatments for cancer and other diseases have created a more immunosuppressed population, says George Thompson, MD, professor of clinical medicine at the University of California, which can make people more susceptible to fungal infections like Valley fever.

Valley Fever Symptoms in Humans

Symptoms are typically mild and flu-like and occur within three weeks of exposure. “In some cases, the infection may also cause joint pain, skin lesions, and rashes,” says John Landry, registered respiratory therapist and CEO of Respiratory Therapy Zone. “If left untreated, Valley fever can spread to other parts of the body, such as the bones, causing more severe symptoms, including bone pain, joint swelling, and inflammation.”

The most common symptoms, according to Cleveland Clinic, include:

The most serious form of the disease is known as disseminated coccidioidomycosis. It’s uncommon, but occurs when the infection spreads beyond the lungs to other parts of the body, including the skin, bones, liver, brain, and heart, per Mayo Clinic.

According to Mayo Clinic, signs and symptoms of disseminated disease will vary depending on what parts of your body were impacted, but may include:

It is important to note that not all individuals with Valley fever will experience symptoms, and some may only experience mild symptoms that resolve on their own. “However, it is still important to seek prompt medical attention if you believe you may have contracted the infection, as early treatment is key to managing symptoms and preventing complications,” Landry adds.

Valley Fever Symptoms in Dogs

Similar to humans, Valley fever can take two main forms of disease in dogs, according to VCA Animal Hospitals: the primary disease and the disseminated disease.

The primary disease is typically limited to the lungs and presents as the following symptoms, per VCA Animal Hospitals:

These signs tend to occur about three weeks after infection, the VCA states. But the organism can also be present in the body for up to three years before showing signs.

In the disseminated disease, the fungus has spread primarily affecting the bones and joints. Symptoms can include the following, per the VCA:

Is Valley Fever Contagious?

Valley fever isn’t a contagious disease, per the CDC. Infection occurs when a fungal spore is inhaled. The spores become airborne when the soil is carried in dust particles by the wind.

How to Test For Valley Fever

To diagnose Valley fever, a healthcare provider will typically order a blood test to detect antibodies or antigens to the fungal spores, explains Oladele Ogunseitan, PhD, MPH, University of California presidential chair, professor of population health and disease prevention. “Microscopic analysis of tissue biopsy and culturing (growing) of the fungus from tissue samples can confirm infection,” he adds. “And chest X-rays or CT scans of lungs can also detect pneumonia due to Valley fever.”

Valley Fever Treatment

Treatment for Valley fever in humans can vary depending on the severity of the infection. In mild cases, at least 95 percent of patients with the fever fully recovered without treatment, according to the Valley Fever Center for Excellence (VFCE). In more severe cases, antifungal medication may be prescribed to help clear the infection. The “azole” family of antifungal drugs (commonly fluconazole or itraconazole) are frequently used to contain the fungus from spreading outside of the lungs but can’t kill it, per VFCE.

In some cases, where the infection has spread to other parts of the body, such as the bones, surgery may be necessary to remove the infected tissue. “Treatment for Valley fever can be a long and challenging process, often requiring months or even years of medication and close monitoring by a healthcare provider,” Landry says. “However, with proper treatment and care, many patients are able to make a full recovery.”

Valley fever in dogs will typically “require lengthy treatment with antifungal medications,” per VCA Hospitals. The length of treatment will be determined by the severity of the infection and in many cases it can last between 6-12 months. In some cases (like if the nervous symptom has been impacted), your furry friend may need to stay on the anti-fungal medication for the rest of their life.

How to Prevent Valley Fever

The best way to prevent Valley fever is to avoid exposure in the first place. The CDC recommends taking the following steps to reduce risk, particularly if you live in an infected area:

No vaccines for Valley fever are available at the time. Though, scientists are currently conducting clinical trials for a human vaccine and the vaccine for pets could be released within the next year.

Alexis Jones is the senior health and fitness editor at PS. In her six years of editorial experience, Alexis has developed passions and areas of expertise around mental health, women’s health and fitness, racial and ethnic disparities in healthcare, and chronic conditions. Prior to joining PS, she was the senior editor at Health magazine. Her other bylines can be found at Women’s Health, Prevention, Marie Claire, and more.

Melanie Whyte was a contributing staff writer for PS. Based in NYC, she writes about LGBTQ identity, sex and relationships, pop culture hot takes, mental health, and home improvement. Her work has been featured by Refinery29, Real Simple, Apartment Therapy, Southern Living, Coveteur, NPR, and more.