In the popular new HBO series The Last of Us, based on the hit video game of the same name, people become zombies after being infected with a fungus similar to the real-life Ophiocordyceps fungus, which can commandeer the bodies of ants.
While the threat of a fungal zombie apocalypse is pure science fiction, illnesses caused by fungi are becoming more widespread, and research suggests that climate change is a key driver in their proliferation.
The California Office of Environmental Health Hazard Assessment reports that cases of coccidioidomycosis infection, commonly known as valley fever, have increased almost fivefold over the past 20 years.
What Is Valley Fever?
A person contracts valley fever by inhaling spores of the Coccidioides fungus, which is present in the soil in parts of the southwestern United States. Currently about 97 percent of all U.S. infections are recorded in Arizona and California. Indeed, the illness gets its name from California’s San Joaquin Valley.
The fungi spores enter the air when the soil is disturbed by strong winds or activities like farming, construction, and biking or ATV traffic over dry soil. Once in the air, the fungus spores can infect the lungs, causing respiratory symptoms such as cough and shortness of breath, as well as fatigue, fever, headache, night sweats, muscle or joint aches, and a rash on the upper body or legs, according to the Centers for Disease Control and Preventions (CDC).
About 60 percent of people who get infected have no symptoms or only very mild flu-like symptoms and do not see a doctor, the agency says. In more serious cases, however, symptoms may take months or even over a year to resolve.
The CDC estimates that between 5 and 10 percent of people with valley fever develop serious or long-term problems in their lungs. In just 1 percent of cases, the infection spreads from the lungs to other parts of the body, such as the brain and spinal cord, skin, or bones and joints — which can be life-threatening.
Every year in the United States there are about 200 deaths related to the disease. Just over 20,000 valley fever cases were reported in 2019, according to the federal health agency.
The Valley Fever Center for Excellence at the University of Arizona stresses that this type of infection is not at all contagious — it cannot be transmitted from one human to another, unlike COVID-19 or the flu.
Climate Change May Be Causing Fungus to Mutate and Expand the Areas Where It Can Thrive
Research published in January in the Proceedings of the National Academy of Sciences found that rising global temperatures and climate change may be playing a role in the rise of fungus-related illness.
On the basis of lab analyses of the effects of heat stress on another disease-causing fungus, Cryptococcus deneoforman, study authors from the Duke University School of Medicine concluded that higher heat conditions on the planet may be speeding up genetic mutations in fungi. These genetic changes allow fungi to have greater heat resistance and greater disease-causing potential.
“Increasing global temperature may affect the fungal evolution in unpredictable directions,” said Arturo Casadevall, MD, PhD, the chair of molecular microbiology and immunology at Johns Hopkins University in Baltimore, in a press release.
Dr. Casadevall, who was not involved in the study, added, “As the world warms, transposons [genetic elements] in soil fungi like Cryptococcus neoformans could become more mobile and increase genomic changes in ways that could enhance virulence and drug resistance. One more thing to worry about with global warming.”
Scientific modeling published the August 2019 issue of GeoHealth predicted that temperature increases and shifts in precipitation may cause valley fever infections to climb by 50 percent by the year 2100, as the fungus expands further northward into drier western states like Idaho, Wyoming, Montana, Nebraska, South Dakota, and North Dakota.
“Climate change is causing more extremes in weather, so you’re getting conditions where the soil becomes extremely dry. [Then] the soil gets kicked up by the winds, spreading more fungus spores,” says Afif El-Hasan, MD, a pediatric asthma doctor with Kaiser Permanente San Juan Capistrano in Southern California and a spokesperson for the American Lung Association. At the same time, while the dry periods help the spores to spread, extreme wet periods help the fungus to grow, he says.
Valley Fever Is Often Underrecognized and Misdiagnosed
Valley fever may be misdiagnosed because its symptoms are similar to those of other respiratory illnesses.
“A lot of fungus infections are mistaken for bacterial infections, and the doctors end up treating what they think is a bacterial pneumonia,” says Dr. El-Hasan. “I think some doctors have a knee-jerk response if there’s a problem in the lungs, and they treat it with antibiotics for a bacterial infection, when they actually need antifungal treatment.”
The disease has also been confused with cancer, tuberculosis, chronic obstructive pulmonary disease, and chronic fatigue syndrome, according to the Valley Fever Center for Excellence.
The center adds that the illness can be confirmed with a blood test, and doctors may also check a patient’s lungs with a chest X-ray, inquire about travel history through the Southwest, or possibly perform a skin test that can detect exposure to the fungus.
El-Hasan urges doctors to consider the geographic area where patients work and what jobs they hold, because in some occupations — such as farming, construction, and firefighting — employees are more likely to breathe in harmful fungus spores.
The most vulnerable are the very young, the elderly, and people with weakened immune systems, according to El-Hasan.
Can You Prevent Valley Fever?
Although vaccines are in development, there is no shot to protect against valley fever. People who work or live in high-risk environments with blowing dust may consider wearing a mask for protection.
“With global warming increasing, I expect we’ll be seeing an increase in the frequency of these valley fever cases,” says El-Hasan.
