It seems that we live in a time of unending bad news on jobs, wars, civil rights, political corruption and the environment. The latter especially seems awful because of its dramatic implications for life on Earth. We caught a glimpse of just how dramatic on Wednesday, May 15, when UC Irvine Ecology and Evolutionary Biology Professor Kathleen Treseder presented “Catching Your Breath: How Climate Change Can Alter the Microbiome You Inhale” as part of the Dean’s Distinguished Lecture Series at the university’s School of Biological Sciences.
Treseder began her lecture, which took place in the UCI Student Center, by acknowledging that she’s had an “eventful couple of years” (you can read about that here ). For the next hour, what she said was often alarming–as is much of what we hear when scientists talk of how climate change will affect life on Earth. But her point was clear: hotter, drier weather brought on by climate change will vastly increase the spread of Valley fever, a dangerous and sometimes fatal fungal pneumonia, throughout the Southwest and into the Plains States.
“I love fungi,” Treseder said during her lecture. “There are millions of spores of fungi, but only a few hundred cause problems.”
In this case, it’s the spores from the Coccidioidomycosis fungus, which is what spread Valley fever. About 40 percent of those infected require hospitalization, and the disease can infect other mammals besides humans (it’s often fatal for dogs). If untreated, the disease can spread from the lungs to other parts of the body, including the brain, which is often fatal.
The spores move fastest during dust storms, but really, anyone outside who breathes in the spores can catch it, which is why agricultural workers are especially at risk of infection. Because the spores are so small, Treseder said that regular dust masks are useless in stopping it.
“Climate change can control many aspects of the Valley fever life cycle,” Treseder told the lecture’s few hundred attendees. “Valley fever cases have risen pretty rapidly in the past two decades.”
In the year 2000, there were about 2,000 recorded Valley fever cases, Treseder said. By 2008, that number had risen to more than 7,000. And last year, there were 14,000+ cases. This increase was in excess of population increase, Treseder added. In 2018, the Ventura County Star reported  that cases in that region north of Los Angeles had risen sharply in recent years.
Currently, the Centers for Disease Control (CDC) considers Orange County to be at “low risk” of a Valley fever outbreak. But the research Treseder presented indicates that this will change over the coming century. In fact, her data indicates that by 2095, OC will have a “fairly high incidence rate” of Valley fever. This has vast implications for the county’s future.
Treseder and her researchers discovered that the link between climate change and the spread of Valley fever is actually quite simple. They found that hot, dry temperatures are key (though Valley fever spores thrive in hot, dry climates, when inhaled they actually become yeast-like, which is why they can grow in a person’s very moist lungs). The best areas for Valley fever spores have an annual average temperature of at least 51 degrees Fahrenheit (which is actually a very warm climate) and an annual rainfall of less than 24 inches.
Today, those areas are mostly just California’s Central Valley (hence the name) and the Southwest. But Treseder’s researchers found that over the next century, those climate conditions will spread throughout the entirety of Southern California and well into the Great Plains–areas where there’s virtually no real Valley fever problem today.
But the situation isn’t completely dire. Work on a vaccine to combat Valley fever is progressing, and advance knowledge of where the disease may spread means the CDC and doctors can prepare. Treseder and her researchers have also been working with their counterparts in Mexico, because spores don’t really care about political borders. And in a twist, Treseder’s researchers also found that the warmer drier conditions that make Valley fever spores spread will also likely slow the fungus that causes Fusarium head blight, which has caused billions of dollars in crop losses (that fungus thrives in cooler temperatures).
In recent years, Treseder has also begun reaching out to elected officials to tell them of her findings and recommendations. She said she had no luck reaching former Republican Rep. Mimi Walters, who represented the Irvine area, but often speaks with Democrat (and former UCI law professor) Katie Porter, who was elected to that seat in 2018.
“It’s not enough anymore to just publish findings in academic journals,” Treseder said.