Valley Fever Spreads in California as Winter Rainstorms Intensify and Summers Heat Up

From dusty fields in the San Joaquin Valley, fungal spores are wafting up, exposing more and more farmworkers to the disease.

Credit: National Geographic Image Collection via Alamy Stock Photo

As rains pummeled the grapevines and tomato plants growing in California’s Central Valley last winter and spring, minuscule fungi thrived in the wet soil. Then the wet weather subsided, temperatures soared to 100 degrees, and the soil grew dusty.

Dry conditions cause the long, skinny strands of the Coccidioides fungus to break apart into even tinier pieces called spores. Then high winds and farm equipment and vehicles digging at the loose earth loft these spores into the air. Increasingly, the region’s farmworkers are inhaling the fungi and falling sick with San Joaquin Valley fever—commonly known as Valley fever.

A few weeks after fungal spores reach the lungs, coughing and flulike body aches can begin. If left untreated, the infection can lead to pneumonia; the Centers for Disease Control and Prevention (CDC) notes the disease causes up to one in three cases of community-acquired pneumonia (i.e., cases caught outside a hospital) in the Southwest. The sick often miss days of work, become hospitalized, and are prescribed strong, pricey antifungal medications. In a small number of cases, Valley fever infection can spread to the joints, spinal cord, and other body parts and cause skin lesions and other painful symptoms.

Every year in the United States, about 10,000 cases of Valley fever are reported and 200 people die from the infection. (Dogs and livestock can also get it.) The disease poses the greatest health threat to residents of south-central Arizona and the San Joaquin Valley of California (where it was originally discovered). Cases have risen substantially since 1995 in those areas, says Orion McCotter, an epidemiologist with the CDC who studies fungal diseases. That year, Valley fever became officially recognized as a national notifiable disease. And the numbers may be much higher than what’s reported, since people who fall ill often get misdiagnosed as having bacterial pneumonia. In fact, the CDC estimates 60 to 80 percent of patients are given one or more rounds of antibiotics—useless ammunition against the fungus.

The reasons behind the growth in reported Valley fever cases are not entirely known, and there is a variety of potential culprits, says McCotter. He notes that more people with weakened immune systems may be traveling and working in areas where they are exposed to Coccidioides (one study notes that Arizona is seeing an influx of elderly residents coming to the state to retire, and tourism has been on the rise in the Southwest generally); in addition, public health officials have gotten better at detecting and reporting the disease. Last, environmental factors such as temperature and rainfall—which can affect the growth of the fungus and how much of it is circulating—likely play a role.

“Climate change may be exacerbating California’s normal whiplash between very wet and very dry conditions,” says Juanita Constible, a senior advocate in NRDC’s Climate and Clean Energy program. “That’s the perfect setup for Valley fever: Ample rainfall promotes the growth of the fungus in soil, and drought leads to more dust and fungal spores in the air.”

Morgan Gorris, an earth system scientist who studies the relationships between climate and human diseases at the University of California, Irvine, points to the particularly wet winter that befell the San Joaquin Valley beginning in December 2016. The rains, which lasted until February 2017, followed several years of drought. And in that year and into 2018, diagnoses of Valley fever in area residents hit a record high.

The disease’s 2017 spike marked the first time California had more cases of Valley fever than Arizona—or any other state. From 2017 to 2018, rates of new cases climbed another 10 percent, according to the California Department of Public Health. Gorris predicts the heavy rainfall this past winter may lead to a new record again this year.

Constible points out another reason the San Joaquin Valley has become a hot spot for the disease: the area’s intense agricultural activity. “All that big farm equipment and those concentrated animal feedlots kick a lot of dust into the air,” she says.

Credit: CDC

People who work outdoors amid the dust, such as construction workers and farmworkers, may be at greater risk of contracting the disease. Those laboring in really dusty conditions might need to wear respirators to protect themselves from Valley fever—but such gear can also make them more susceptible to heat-related illnesses. Those, too, are becoming more common under climate change.

Disease experts fear that limited access to both public health information and medical care may exacerbate the risks to farmworkers. Many people who plant and pick food in the San Joaquin Valley migrated there from elsewhere and may not have heard of Valley fever. “They won’t know to seek medical help early if they become sick, especially since Valley fever often resembles the flu,” Gorris says. “If the disease starts to spread outside the lungs, this can cause a more complicated form of the disease.” Moreover, he adds, “Many farmworkers work long, late hours, and by the time they are done working for the day, local health clinics are closed.” They may not have the time, health insurance, or financial resources to seek medical help—and a Valley fever diagnosis can send medical bills skyrocketing.

Valley fever costs patients with pneumonia an estimated $22,000; for severe forms of the disease that have spread outside the lungs, the cost can soar to approximately $1,024,000, according to a study published this year by researchers from the University of California, San Francisco. The authors estimate that the total lifetime cost burden of cases reported in 2017 in California could reach nearly $700 million.

Last year, as part of the final state budget signed during his tenure in office, California Governor Jerry Brown allocated $8 million for Valley fever research. Advocates for the funding included Democratic assemblyman Rudy Salas, whose district includes Bakersfield in Kern County, where the largest number of Californians suffer from the disease each year.

Meanwhile, the CDC, California Department of Public Health, and local health departments are working together to make health care providers more aware of Valley fever and more proficient in testing for it. “We are hopeful that these awareness efforts will help encourage doctors to ‘Think Fungus’ when symptoms of infection do not get better with antibiotics,” McCotter says, quoting the motto of the upcoming Fungal Disease Awareness Week. The CDC is working to get rapid diagnostic tests for Valley fever into more health clinics, since earlier diagnosis can prevent inappropriate treatments and keep simple cases from becoming complicated ones. Disseminating public information about the disease can also help those who do grow sick to recognize their symptoms faster, McCotter says, and seek help.

But much about the disease remains a mystery. Scientists don’t know how long the spores can survive in a hot and sunny environment or how far they can travel, Gorris says. “The Valley fever community still has a lot to learn about where the fungus grows, why certain people become sicker than others, and the best treatment for the disease, so research funding is invaluable.”

Public health agencies and the health care sector also have a lot of catching up to do. In June in Atlanta, NRDC helped organize a National Drought and Public Health Summit that brought together government officials from the local, state, and federal levels as well as tribal representatives, public health advocates, and members of the academic community. Participants discussed ways to protect Americans from health hazards —including infectious fungi—associated with drought.

The event was a wake-up call to many about the extent to which Valley fever is on the rise, with no easy solutions. As Constible warns, “Exposure to Valley fever is one of many ways climate change can affect human health, and most health agencies, hospitals, and other providers are woefully unprepared for our climate-disrupted world.”

This story is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the story was originally published by and link to the original; the story cannot be edited (beyond simple things such as grammar); you can’t resell the story in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select stories individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our stories.

Related Stories