Jose Epifanio Sanchez Trujeque rests in Bakersfield, California, in 2023 after contracting Valley fever, which led to meningitis and a stroke. The fungal disease is a growing risk in the state.
Photo by Fat Camera, courtesy iStockphoto
Two years ago, health researchers in California warned the state could soon face a surge of Valley fever, a lung infection caused by inhaling spores that grow in the soil. Their study showed that a pattern of years-long drought followed by a wet winter leads to greater transmission of the fungal pathogen.
Their prediction came true. In 2023, following a winter of heavy rain after years of drought, California reported nearly 9,300 cases of Valley fever — more than any other year on record.
The respiratory infection, caused by the fungus Coccidioides, can cause symptoms of pneumonia that last weeks to months. People with compromised immune systems are especially vulnerable to severe illness if they breathe in the spores, which are mostly found in the Southwestern U.S.
Justin Remais, PhD, MS, a lead author of the study and chair of the Division of Environmental Health Sciences at the University of California-Berkeley, said drought conditions actually suppress the disease because the fungus needs water to thrive. But a wet, rainy winter brings it booming back. By the time the dry summer arrives again, an abundance of Valley fever spores are ready to be swept up by the wind.
Climate change could make that pattern more likely by intensifying the conditions that help Coccidioides prosper, Remais said.
“Drought is already an extreme part of the climate that is potentially becoming more extreme and more frequent,” he told The Nation’s Health. “That will have implications for Valley fever.”
Fungal disease, which is increasing worldwide, is one of many health risks expected to worsen due to the effects of climate change, such as hotter temperatures and more intense natural disasters. But compared to viral and bacterial diseases, a lot less is known about fungal ones, making it harder to track, predict and prepare for them.
“For common fungal diseases, we know a lot,” said Arturo Casadevall, MD, PhD, chair of molecular microbiology and immunology at Johns Hopkins Bloomberg School of Public Health. “But there are a very large number of fungal pathogens that are rare and for these, we often know very little.”
CDC Epidemic Intelligence Service officer Amy Xie uses a device to simulate environmental transmission of Candida auris amongst staff members at a Seattle, Washington, long-term acute care facility experiencing an outbreak this year.
Photo by Shauna Clark, courtesy CDC Public Health Image Library
Recent research, published in January in The Lancet Infectious Diseases, estimated a yearly incidence of 6.5 million invasive fungal infections worldwide, leading to about 3.8 million deaths. People with weakened immune systems — such as cancer and organ transplantation patients and those with HIV — are at higher risk of developing fungal infections and having severe complications.
In 2022, the World Health Organization released a report on its inaugural list of 19 fungal priority pathogens that represent the greatest threat to public health. Among them are Cryptococcus neoformans, a soil fungus that can cause meningitis in immunocompromised patients; Candida auris, a multi-drug-resistant yeast; and Aspergillus fumigatus, a mold that attacks the lungs of people with weak immune systems.
“Despite posing a growing threat to human health, fungal infections receive very little attention and resources globally,” said the WHO report. “This all makes it impossible to estimate the exact burden of fungal infections and consequently difficult to galvanize policy and programmatic action.”
Evidence suggests both the incidence and geographic range of fungal infections are growing due to climate change, the report noted.
For example, research shows fungal outbreaks often follow natural disasters such as hurricanes, tornadoes and floods. Other studies find that hotter conditions are allowing pathogenic fungi to adapt to warmer temperatures, which could help them break through people’s natural defenses.
Right now, the human body is too warm for most fungi to thrive in, “so if you have intact immunity, you can keep it out,” Casadevall said. But climate change-induced heat adaptation could give fungi a new chance.
“As they adapt to higher temperatures, we’re going to get new fungal diseases that we don’t even know about,” Casadevall told The Nation’s Health.
He said he suspects that scenario already happened with C. auris, a severe, multidrug-resistant fungal species with a high death rate that mostly impacts immunocompromised people. Evidence suggests that early in the last decade, C. auris emerged independently on three different continents almost simultaneously. A number of factors probably contributed, Casadevall said, but data suggest thermal adaptation is one.
“The common denominator is the world is warmer every where,”he said.
In 2022, the California Environmental Protection Agency added fungal infection — specifically Valley fever — to its list of climate change indicators. State data show incidence of the disease has increased fivefold from 2001 to 2022, with most cases in South San Joaquin Valley, where the disease was first discovered.
Jace White, who acquired Valley fever while farming, stands on his family’s property in Fresno, California. The disease left him so tired he could not walk.
Photo by Carolyn Van Houten, courtesy The Washington Post/Getty Images
Preventing Valley fever infection is difficult, said Erica Pan, MD, MPH, deputy director of the California Department of Public Health’s Center for Infectious Diseases. Anyone can breathe in a spore if they are in the right place at the right time. This summer, for example, the agency identified more than a dozen Valley fever cases tied to an outdoor music festival near the city of Bakersfield.
Pan said a key to the agency’s response and preparedness for Valley fever is raising awareness among health providers so they know to test for the fungal disease in at-risk regions.
John Galgiani, MD, director of the Valley Fever Center for Excellence at the University of Arizona’s College of Medicine-Tucson, agrees. About a decade ago, the center partnered with Banner Health, a health system in Arizona — where the majority of U.S. Valley fever cases occur — to educate its providers about the disease.
Before the intervention, only about 2% of people showing up to urgent care with pneumonia symptoms were being tested for Valley fever, Galgiani said. Post-intervention, he said the rate went up more than 40%, which revealed that many more cases of pneumonia are being caused by Valley fever than were previously diagnosed.
Work on a Valley fever vaccine is underway and if ultimately approved, it would be the world’s first against a fungal infection. But until then, “awareness is our best defense,” Galgiani said.
One factor impeding that awareness is lack of knowledge. Fungal disease reporting varies widely by state and only two — Valley fever and C. auris — are nationally notifiable diseases. The dearth of data makes it hard to get ready for any climate impacts. Remais, at the University of California-Berkeley, hopes to start filling that gap.
Last year, he and colleagues launched one of the most comprehensive studies on the epidemiology of fungal diseases and their relationship to climate change and social disadvantage. The researchers are analyzing nearly 20 years of medical records from almost 100 million U.S. patients to pinpoint where and when fungal diseases emerge and what makes people susceptible.
The five-year project will provide a more detailed picture of seasonal fungal disease patterns and how fungi interact with the environment, Remais said. Ultimately, the findings could help public health workers plan for surges and protect more-vulnerable residents.
“Next, we need to build the infrastructure that can convert this knowledge into more robust preparedness,” Remais said.
For more information on fungal disease and climate change, visit bit.ly/cdcfungusclimate.
- Copyright The Nation’s Health, American Public Health Association
