This story was originally Featured on Grist and part of the Climate Desk collaboration.
Last week, a strip of Earth's atmosphere funneled trillions of gallons of water eastward from the tropical Pacific Ocean and into California. The weather phenomenon, known as the atmospheric river, broke rainfall records, dumping more than a foot of rain on parts of the state and leaving 800,000 residents without power. At least nine people were killed in car crashes or by falling trees. But it could be months before the storm's health effects are fully felt.
Flooding caused by intensifying winter storms in California is fueling the spread of a deadly fungal disease called coccidioid mycosis, or Valley fever. “Hydroclimatic whiplash is seeing increasingly large fluctuations between extremely wet and extremely dry conditions,” said Daniel Swain, a climate scientist at the University of California, Los Angeles. Humans are finding it difficult to adapt to this new pattern. But the fungi are thriving, Swain said. Valley fever is “going to become a bigger and bigger story,” he added.
Valley fever cases broke records in California last year after nine consecutive atmospheric rivers swept through the state, causing widespread and record flooding. Last month, the California Department of Public Health issued an advisory to health care providers reporting 9,280 new cases of Valley fever with an onset date in 2023, the highest number the agency has ever recorded. This was the highest number among all. In a statement provided to Grist, the California Department of Public Health said last year's weather and disease patterns indicate the potential for “an increased risk of Valley fever in California in 2024.”
“When you look at the numbers, it's surprising,” said Shanxin Yang, a clinical microbiologist at the University of California, Los Angeles. “About 15 years ago, we only saw one or two cases a month in our lab. Now we're seeing two or three cases a week.”
Valley fever (named after California's San Joaquin Valley, where the disease was discovered in farm workers in the late 1800s) is caused by spores of a fungus called . Coccidioides. Inhalation of the spores can cause serious illness in humans and some animal species such as dogs. This fungus is particularly sensitive to extreme climates. Coccidioides It cannot grow in areas of the United States that receive year-round rain, nor can it tolerate sustained drought.