Valley fever turning into an epidemic in California: Scientists find a strong link to dogs

Valley fever cases are projected to rise in 2025, especially in California. With the summers incoming, the concerns around the endemic’s spread also raises concerns. Researchers have now found a strong correlation between the disease in canines and people. A new study suggests dogs could help predict the spread of valley fever in humans.
Valley fever, also known as coccidioidomycosis, is caused by a fungus that thrives in moist soils and becomes airborne during drought. These spores are easily inhaled, leading to infection. The climate change of increasing heavy rains followed by prolonged drought could create the perfect conditions for it in the Western United States. A by researchers at the University of California, Davis, published in the Journal of Infectious Diseases, found that dogs, who are also susceptible to the disease, can help us understand its spread.

“Dogs are sentinels for human infections. They can help us understand not just the epidemiology of the disease but they’re also models to help us understand the disease in people,” lead author Jane Sykes, professor of small animal internal medicine at the UC Davis School of Veterinary Medicine said in a statement.
Valley fever is common in animals, especially dogs that dig in dirt. Researchers examined nearly 835,000 blood antibody tests from dogs that had been tested for the infection across the country between 2012 and 2022. Nearly 40% of them tested positive.

They found that Valley fever in dogs spread from just 2.4% of U.S. counties in 2012 to 12.4% in 2022. “We were also finding cases in states where valley fever is not considered endemic. We should be closely watching those states because there could be under-recognition of the emerging fungal disease in humans,” Sykes said.
About 10,000 to 20,000 Valley fever cases are reported in humans every year, as per the CDC, however, the actual numbers could be at least 33-fold higher. Many states do not require the reporting of human cases. The CDC considers valley fever endemic in parts of six states, including Arizona, California, Nevada, New Mexico, Texas, and Utah. The study found valley fever in dogs in those states, and also in Oregon, Washington, Idaho, Montana, Wyoming, and Colorado.

Dog breeds that like to dig are more at risk of getting the disease. Most medium-to-large dogs including terriers are susceptible. The researchers found that dogs also exhibit some signs similar to that of the valley fever sign in humans. This includes cough, as the infection develops in their lungs. The fungus can also spread to the bones, brain, and skin and require lifelong antifungal injections. Dogs can also die from the disease. Hence, understanding the disease in dogs is crucial for knowing how it affects humans.


Sykes stated that dogs are an under-recognized model for understanding valley fever. By learning more about valley fever in dogs, scientists may discover new tests or treatments for the disease in humans. They may also help prevent misdiagnosis or undiagnosed disease in humans.