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Hunting an Underground Epidemic

Sophia Friesen

In 2001, 10 archaeologists working at a dig site in northeastern Utah suddenly fell ill with a respiratory illness that sent eight of them to the hospital, coughing and feverish. The symptoms resembled pneumonia, but their diagnosis was unexpected. It was Valley fever, a fungal infection that spreads to people through spores in the soil and dust—and it wasn’t supposed to be there. Valley fever is more common in hotter, drier states; previous predictions of where the fungus could survive in the soil barely extended into the southwest corner of Utah. The archaeologists’ dig site, in Dinosaur National Monument, was hundreds of miles outside the disease’s expected borders.
The truth is, nobody really knows which areas of the state harbor Valley fever. But the archaeologists’ plight shows that its fungal culprit could be far more widespread than anyone predicted. And as the climate changes, the fungus will likely spread further, explains Katharine Walter, PhD, assistant professor of epidemiology at the Spencer Fox Eccles School of Medicine at the University of Utah.

“There have been incredibly intense recent changes in temperature as well as precipitation and drought here in the American West. These all impact the range of where the fungus can exist.”
Katharine Walter

Walter is on a mission to map where in Utah the Valley fever fungus can survive and predict how it will move across the landscape as the climate changes. Walter and her collaborators—Katrina Derieg, vertebrate collections manager at the Natural History Museum of Utah; Eric Rickart, PhD, adjunct associate professor of biology at the U and curator of vertebrates at NHMU; and Kevin Perry, PhD, professor of atmospheric sciences in the College of Mines and Earth Sciences—recently received a $375,000 Climate and Health Interdisciplinary Award through the Burroughs Wellcome Fund to power their fungus hunt and raise awareness of what to do for the people most at risk of infection.

Two figures stand in a vast, scrub-covered flatland with huge mesas and mountains in the blue distance
Perry (left) and Derieg (right) check for samples outside Santa Clara, UT. Image credit: Katharine Walter.

Tracking the Invisible

Valley fever is a tough disease to track down. The fungus that causes it doesn’t spread from person to person but instead grows stealthily in the soil, never emerging above the surface. “When most people think of fungus, they think of mold or mushrooms, something that you can see,” Derieg explains. “But this is not a fungus that has any kind of visible fruiting body. It can only be identified with a microscope, which makes it really tricky to identify in the field.” 
When it does infect people, lack of awareness of the disease by affected populations and medical professionals means that it often goes undiagnosed or misdiagnosed, causing delays in necessary antifungal treatment for those who are seriously ill.
To try to map the spread of the fungus, the researchers are collecting soil and dust samples from a wide range of Utah climate zones and testing them for fungal DNA. They’re also searching for traces of the fungus in rodents, like pocket mice, that burrow underground. At least some rodent species carry Valley fever, and while they don’t transmit the disease directly to humans, the scientists suspect that they are instrumental in moving the fungus into new areas of the soil.

Interior of dusty tent packed with notebooks. Through the open door, a man in a cowboy hat bends over a sample box in front of blue sky and red mesas.
Rickart in the field outside Santa Clara, UT. Image credit: Katrina Derieg.

A Fever Hotspot

The research team is focusing its efforts on the region with the highest reported prevalence of Valley fever in the state: Washington County and especially St. George. There, in the fastest-growing metropolitan area in the nation, rapid construction is churning up previously undisturbed areas of the Mojave Desert at unprecedented speed, kicking up large quantities of potentially spore-laden dust. Where others see future housing developments, the researchers see the potential for a spike in disease cases.
Another reason the researchers are focusing on Washington County is its dramatic landscape. The topography spans elevations ranging from the lowest point in Utah all the way up to Signal Peak. This 8,000-foot elevation range encompasses a huge variety of microclimates that serve as stand-ins for the diverse climates across Utah. Sampling a relatively small region in Washington County can give the researchers a picture of where the fungus can thrive statewide. The scientists will combine their knowledge of which environments support the fungus with predictions of how the climate will change over time, gaining an understanding of which areas are at risk now and which will be in the future.

Rocky creek flowing between mesas beneath a cloudy sky.
Landscape outside Toquerville, UT. Washington County's dramatic landscape makes it a proxy for many climates statewide. Image credit: Katrina Derieg.

Reaching Out to Those at Risk

The researchers also aim to raise awareness about the risks and symptoms of Valley fever. “An important component of this project is to educate the public to let them know what is in their community, what signs they should be looking for, and how they can prevent it,” Perry says. Armed with this awareness, people in fungus-ridden regions of the state could reduce their risk by wearing a dust mask on dry, windy days when spores are more likely to be airborne. And doctors who know the signs and symptoms of Valley fever are more likely to catch the disease early and start antifungal treatments if necessary.
Even within regions where the fungus is in the soil, specific populations are differentially vulnerable to Valley fever, Walter says. “Because we get sick by inhaling fungal spores that are found in the soil, people who work outside in jobs like construction, agriculture, and firefighting are at extremely high risk of infection and disease,” she explains. “Valley fever is very much an increasing health justice and environmental justice issue.” Previous research has also shown that incarcerated people tend to be at particularly high risk of the disease, perhaps due to dust exposure on prison grounds.
Walter adds that, while serious, Valley fever is far from the only disease that will change as the climate shifts. “This is just one example of an infection that will be, and is already being, dramatically impacted by climate change. There are many others. And the consistent theme is always that the most vulnerable populations are put at highest risk. The urgency of this issue really can’t be overstated... Valley fever is just one component of this storm we're all living through."

Five people hike across a dusty lot surrounded by mesas and mountains.
The research team outside Toquerville, UT. Left to right: Kimberly Hanson, MD; Kevin Perry, PhD; Alyssa McCoy; Katrina Derieg; Schuyler Liphardt, PhD. Image credit: Katharine Walter, PhD.
Four profile photos: a woman with a microscope, a man with salt flats in the background, a woman in the woods, and a man with a mustache
Left to right: Katharine Walter, Kevin Perry, Katrina Derieg, and Eric Rickart.