California could face another record-breaking year of Valley fever fungal infection

NBC News

20-05-2025

Brynn Carrigan's headaches started in April 2024. Within a couple of weeks, she was debilitated.
Her vomiting exacerbated the excruciating pain in her skull. She spent nearly every hour in bed with the covers pulled over her head, blocking out any sliver of light. Even the clock on her microwave was too much.
'I went from training for a marathon, raising two teenagers and having a job to essentially being bedridden,' said Carrigan, 41, of Bakersfield, California, who works for Kern County Public Health.
Her condition continued to get worse and doctors couldn't provide answers — until her third visit to the hospital, when one doctor asked her if she'd had any respiratory symptoms before the headaches started.
She had. About a month before the headaches started, Carrigan had what she thought was a typical cold — though she recalled that her cough lingered a bit longer than normal and she went on to develop a rash on her thighs. Both symptoms got better without treatment.
These turned out to be key pieces of information. A biopsy of her spinal fluid revealed that Carrigan had coccidioidal meningitis, a rare complication of a fungal infection called Valley fever.
'I knew something was wrong but never in a million years did I think it would be something so serious,' Carrigan said.
Valley fever, or coccidioidomycosis, is caused by inhaling coccidioides spores, a type of fungi endemic to the hot, dry climate of the southwestern United States. Climate change is creating drier soils that are inching farther east, expanding the range of the fungi. Valley fever is increasingly being diagnosed outside its usual territory and cases have been rising across the Western U.S. While Arizona still sees the highest number each year, California is closing the gap.
From 2000 through 2016, California had 1,500 to 5,500 cases a year. From 2017 through 2023, those numbers jumped to 7,700 to 9,000 annual cases. Preliminary data for 2024 puts the count at more than 12,600 — the highest the state has ever seen and about 3,000 more cases than the previous record, in 2023.
Early data shows California is on track for another record-breaking year. Already, the state has logged more than 3,000 confirmed cases of Valley fever statewide, more than there were at the same time last year and nearly double what cases were at this time in 2023.
'There is no question that the number of cases of coccidioidomycosis is enormously higher than before,' said Dr. Royce Johnson, chief of the division of infectious disease and director of the Valley Fever Institute at Kern Medical in California. 'If you want to see me, right now you'd have to wait until July, and that goes for my colleagues, too.'
Drought cycles driving spread
Carrigan lives in Kern County, a dry, sprawling region that sits between two mountain ranges at the southern end of California's Central Valley.
The county has already recorded at least 900 Valley fever cases so far this year and has been ground zero for the fungal infection in the state for the last three years.
But the consistently high cases in places like Kern County are not driving the upward trend in California, said Gail Sondermeyer Cooksey, an epidemiologist at the California Department of Public Health.
Instead, new hot spots are emerging along the edges of the Central Valley — in Monterey and San Luis Obispo counties, along California's central coast. Cases in Contra Costa County, just east of Berkeley, have tripled so far this year compared with the same time in 2023.
'It appears to be spreading out,' Sondermeyer Cooksey said.
Many factors likely influence how well coccidioides spores multiply and spread, 'but one thing we have identified as a big driver of those peaks and dips is drought,' she said.
A 2022 study in The Lancet Planetary Health found that drought years suppress Valley fever cases, but multiple years of drought followed by a wet winter causes cases to rebound sharply. This shift in weather patterns, which is driven by climate change, appears to largely influence where new Valley fever hot spots emerge. Longer, drier summers can also shift transmission season, when the spores spread, from late summer and early winter to earlier in the year.
'We're seeing wetter wets and drier dries across the Southwest, but California is seeing that to a higher degree,' said Jennifer Head, an assistant professor of epidemiology at the University of Michigan, who studies Valley fever and climate change.
In Arizona, new hot spots are popping up in places in the state that have a climate more similar to California's than elsewhere in Arizona.
'The highest increases in Arizona are in the northern plateau regions, which, similar to California, have historically been colder and wetter,' Head said.
Closely tracking Los Angeles
The climate patterns expanding Valley fever's range in California are the same ones that drive increasingly intense wildfires. Scientists are still trying to understand how fires may worsen Valley fever risk, but some research has shown a link between wildfire smoke and higher rates of diagnoses.
Sondermeyer Cooksey said the state health department warned first responders to January's devastating fires in Los Angeles County of the potentially increased risk of Valley fever in the area because of the fires. There have been past outbreaks among wildland firefighters.
There's some limited evidence that wildfires may spread the coccidioides spores. In a 2023 study, researchers looked at 19 fires across California and observed higher rates of Valley fever following three of those fires. These fires tended to be larger, located near population centers and burned areas that had high Valley fever transmission prior to the fire.
'It's not entirely clear whether there is a link between wildfires and Valley fever, but what is important to know is that coccidioides live in the dirt and anything that disturbs the dirt can exacerbate Valley fever,' Sondermeyer Cooksey said. 'Fires do that, then we have all of the reconstruction projects that also disturb soil.'
Peak Valley fever season hasn't happened yet this year. Because reconstruction efforts are disturbing soil in the burn scar, Sondermeyer Cooksey said state and local public health departments 'are closely tracking the numbers' in areas hit by January's fires.
Cases after Lightning in a Bottle festival
Diagnosing Valley fever is tricky, mostly because its symptoms overlap with other respiratory illnesses including flu, Covid and pneumonia. If someone experiences those symptoms, it's important for them to let their doctor know if they've been around disturbed soil or dust — in a construction zone, camping, hiking, working outside or at a festival — or in an area known to have Valley fever, Sondermeyer Cooksey said.
Symptoms typically show up one to three weeks after exposure, but it can take as long as eight weeks, so people may not make an immediate connection, Head, of the University of Michigan, said.
Last year, at least 19 people who attended the Lightning in a Bottle music festival — which is being held in Kern County again this month — were diagnosed with Valley fever later in the summer. At least eight were hospitalized.
'Lightning in a Bottle is right in the middle of the endemic region, that's one of the hot spots for the disease,' said Dr. George Thompson, director of the Center for Valley Fever at the University of California, Davis, adding that the vast majority of people who attend will not get an infection, but people who aren't from an endemic area may be at higher risk.
Thompson said it's clear that he and his colleagues across the state are treating more patients for the infection. Only about 1% of cases result in life-threatening meningitis or other complications, as Carrigan's did, but once a person is infected, they never clear the fungus from their body.
'There is no drug that kills cocci, so what keeps you from being ill is your immune response,' Johnson, of Kern Medical, said. To treat the infection, people are given antifungals 'long enough for a person's immune system to figure out how to control it. If you then do something to disrupt that immunity, it can start growing again, and that can surface years later,' he said.
Carrigan spent the last year on an intense regimen of anti-fungal treatments. During the first few months, she lost most of her hair and eyelashes and barely recognized herself in the mirror.
She's now made a full recovery and even ran a marathon this spring, but she still takes anti-fungal medication. Carrigan said she wants more people to understand both the warning signs of Valley fever and the importance of telling their doctor if they've been somewhere with cases, which could help people get a faster diagnosis.