What is valley fever and how does it spread?

Valley fever is an infection spread by a fungus that grows in the top few inches of soil in parts of the American West. It is transmitted when soil is disturbed and the fungal spores become airborne. People and animals — like dogs, cats, sheep, and cattle — become sick by inhaling the spores. Valley fever cannot be passed from person to person.

The disease primarily affects the lungs, but it can also spread to other parts of the body. While most people will have mild or even no symptoms, some people become very sick and require hospitalization.

The epicenter of the disease is the U.S. Southwest, including Arizona and Southern California, but the fungus, called Coccidioides, is found as far north as Washington state and south into Mexico, Central America, and parts of South America. The fungus has recently been found in other parts of the Western U.S., which may be due in part to climate change producing environmental conditions that fuel its growth.

Who’s most at risk?

Anyone who lives in, visits, or works in the areas where the fungus exists can get valley fever. People who work in agriculture, construction, and other activities that involve working in or around disturbed dirt and outdoor dust are at higher risk.

Certain demographics are also at higher risk for more advanced forms of the disease. Those include men, people of African and Filipino descent, women in their third trimester of pregnancy, HIV/AIDS and cancer patients, and those who are immunosuppressed.

How can you prevent valley fever infection?

There is no means of prevention, though using N95 masks in dusty areas where the fungus grows can help reduce your risk. A vaccine for dogs is expected to be available as early as the end of 2025, and a human vaccine is currently in early-stage development.

What are the symptoms of valley fever, and how is it diagnosed and treated?

Symptoms may include a fever, cough, chills, tiredness, night sweats, headache, shortness of breath, joint and muscle pain, and a rash. In severe cases, the disease may spread to other parts of the body, including the skin, bones, joints, and brain.

Valley fever is diagnosed with a blood test and doctors can also use imaging to examine the disease’s spread. Without the blood test, valley fever can be misdiagnosed as cancer, tuberculosis, or other diseases.

While some valley fever infections go away on their own, doctors can prescribe anti-fungal drugs, which suppress symptoms but do not kill the fungus. The immune system is ultimately responsible for improving patients’ symptoms, so doctors recommend rest and good nutrition as patients recover.

What’s being done to address valley fever?

The National Institutes of Health, the federal government’s medical research arm, has awarded researchers in three states millions of dollars to research new antifungal drugs, design rapid tests, and better understand why some people develop the severe form of valley fever while others experience no symptoms. 

At the Valley Fever Center for Excellence in Arizona, experts who have spent decades studying the disease are working with public health officials and hospitals across the state to make sure people affected by valley fever get their diagnoses more quickly. Researchers in California and Arizona are working on a surveillance system that merges real-time weather conditions and construction activity to pinpoint where people are most at risk of breathing in airborne spores. 

There are at least four different research initiatives underway to discover and design an effective vaccine. The jab closest to becoming reality, which is being developed by a pet pharmaceutical company called Anivive Sciences, entered the first of several stages of development for human use last year.