Persistent respiratory symptoms that evade diagnosis? It could be this growing environmental threat
Industry Buzz
We’re really trying to encourage providers to take a travel and work history when they see patients with prolonged respiratory symptoms.
—Gail Sondermeyer Cooksey, MPH
Coccidioidomycosis, or Valley fever, has mainly been found in Arizona, California, Nevada, and New Mexico. Today, changes in weather patterns and soil disruption from construction and agriculture seem to be driving increased cases across multiple Southwest states. [] []
As incidence rises and the geographic footprint expands, clinics in both endemic and newly affected areas may see more patients with persistent respiratory symptoms that are difficult to diagnose, making awareness and early recognition increasingly important for front-line providers. Here's what you need to know for the clinic.
What is Valley fever?
Valley fever is caused by the fungus Coccidioides immitis or Coccidioides posadasii. [] Both are soil-dwelling fungi that thrive in dry areas; when soil is disturbed, their spores can be dispersed through the air and can cause illness when inhaled.
According to the California Department of Public Health, some infected individuals will develop mild illness, while others will experience more severe disease. [] About 1% of patients will develop disseminated disease, which can be fatal.
“Not every patient with Valley fever is going to need treatment. But it is important to monitor patients, and sometimes patients will be monitored for months or years for signs of severe disease: worsening respiratory illness; progression to the skin, bone, and joint infection; or meningitis,” Gail Sondermeyer Cooksey, MPH, an epidemiologist at the California Department of Public Health, tells MDLinx.
Increased Valley fever rates
In California, Valley fever incidence has increased more than fivefold from 2001 to 2021, and the state reported nearly 12,500 cases in 2024. [] []
Research suggests that rainfall patterns are one important factor. [] “The main pattern we found is that when we have several years of drought followed by a wet winter, we then have a large surge in Valley fever in 2 to 3 years after that time period,” Cooksey says.
Human activities, such as construction and agriculture, can increase the likelihood that Coccidioides spores will enter the air and be inhaled. []
“Most cases in California—historically and still today—are reported in the Central Valley, which is where Valley fever gets its name, and also in our Central Coast region. But it’s really important for providers to know that it is moving into more areas where it didn’t used to be common. We’ve seen some really large increases as far north as the northern San Joaquin Valley and even into parts of the Bay Area, and we’ve also seen increases in more parts of the Central Coast and also into Southern California,” Cooksey notes.
Elsewhere in the Southwest, Southern Arizona remains a hot spot, with the US’s highest Valley fever incidence, but Northern Arizona counties have also seen an increase in infections. [] []
Cases have also risen in New Mexico, though incidence there remains lower than in Arizona or California. Valley fever infections also occur in Utah, Texas, Nevada, and (rarely) Washington state.
When to think about Valley fever
“It can be challenging to diagnose Valley fever because it mimics a lot of other common illnesses, like COVID-19, influenza, or even tuberculosis or a malignancy if it’s [a] disseminated disease,” Cooksey says. “We really think about it if someone’s had prolonged respiratory disease lasting more than 10 days; if they’ve lived, worked, traveled, or [gone] to school in an area where it’s common; and especially if that patient’s been around outdoor dirt and dust or has worked outdoors.”
While anyone can get Valley fever, the risk factors for severe disease include being pregnant, having a weakened immune system, being older, and being of certain races (people from the Philippines and Africa are at greater risk). []
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