People living hundreds of miles from Arizona and California are now at risk of contracting Valley fever, a fungal lung infection historically confined to the desert Southwest. The CDC recorded 21,037 reported cases of coccidioidomycosis across the United States in 2023, and national statistics on Valley fever show that cases have turned up in states far outside the traditional hot zone. Environmental sampling has confirmed the causative fungus, Coccidioides, in the soil of Washington state counties, while outbreak investigations and soil DNA detections in northeastern Utah demonstrate that the pathogen has already established itself in places most clinicians would never think to look.
Why the fungus is spreading beyond its historic range
Valley fever has long been treated as a regional problem. Arizona and California account for the bulk of reported infections, and doctors in other states rarely consider the diagnosis. That assumption is breaking down. In 2013, researchers identified Coccidioides immitis in soil samples collected from south-central Washington, a finding tied to suspected locally acquired human cases in the same area. The Washington State Department of Health has since confirmed the fungus through environmental sampling in Benton, Kittitas, and Yakima counties, while noting that the full geographic range remains under investigation.
The question is not simply whether Coccidioides exists in new places but whether soil disturbance in those places will generate clusters of disease. Construction, agricultural tilling, and archaeological excavation all kick fungal spores into the air. A point-source outbreak among workers at an archaeological site in northeastern Utah showed exactly that mechanism at work: people digging into soil in a location no one considered endemic fell sick with coccidioidomycosis. Separate laboratory work detected Coccidioides DNA in soil at Dinosaur National Monument, reinforcing the idea that the fungus occupies parts of Utah well north and east of the state’s arid southwest corner.
Counties that are seeing rapid housing development or infrastructure expansion on newly suitable land face a concrete near-term risk. If climate conditions continue to shift and soil disturbance accelerates in these areas, state notifiable-disease registries could begin recording measurable clusters of locally acquired infections within a few years, well before national case totals spike in a way that draws federal attention. The pattern in Washington, where suspected local cases prompted the soil investigation, offers a preview of how detection will likely unfold: a handful of puzzling pneumonia cases that do not respond to antibiotics, followed by belated testing for a fungus no one expected to find.
Soil data, case counts, and climate projections
Several independent lines of evidence support the conclusion that Valley fever’s range is widening. CDC surveillance covering 2011 through 2017 documented coccidioidomycosis cases reported in states outside Arizona and California, and a subsequent 2019 surveillance summary highlighted the importance of detecting exposures among people living in areas not previously known to be endemic. Within Arizona itself, a CDC analysis of incidence from 2005 through 2022 linked regional increases to aridity, warming temperatures, and volatile precipitation patterns, the same environmental drivers that climate models project will expand into new geographies.
Peer-reviewed climate niche modeling published in GeoHealth has projected that warming scenarios will push the boundaries of suitable Coccidioides habitat into additional counties and states across the western and central United States. Utah’s own epidemiologic record backs up that trajectory. An analysis of Utah Department of Health case data from 2006 through 2015 found that coccidioidomycosis incidence varied across the state during 2009 to 2015, with cases appearing in areas beyond the historically emphasized southwest corner. Combined with the Dinosaur National Monument soil findings and the archaeological-site outbreak, the Utah data make clear that the fungus is not waiting for models to catch up.
The Washington evidence is equally direct. The state’s Department of Health treats coccidioidomycosis as a notifiable condition and has documented soil isolation in south-central counties, establishing that the pathogen can persist in Pacific Northwest soils. Suspected locally acquired human cases in the same region close the loop between environmental presence and actual disease transmission.
Gaps in surveillance and what to watch next
For all the evidence pointing to geographic expansion, significant blind spots remain. Post-2017 CDC case-level data that distinguish confirmed local acquisition from travel-related infections in newly reporting states have not been published in a form that settles where people are actually picking up the fungus. A traveler who visited Phoenix and later tests positive in Nebraska looks very different, epidemiologically, from a construction worker who never left Yakima County. Without systematic exposure-source interviews and consistent case definitions, public-health agencies cannot easily separate imported infections from those signaling new endemic foci.
Another challenge is underdiagnosis. Valley fever often presents as a nonspecific pneumonia-like illness with fever, cough, and fatigue. In regions where clinicians are unfamiliar with the disease, patients may receive multiple courses of antibiotics before anyone considers fungal testing. Serologic assays are not always ordered, and even when they are, follow-up may be incomplete. This diagnostic lag obscures the true footprint of the disease and delays recognition of emerging hotspots.
Laboratory capacity and reporting infrastructure further complicate the picture. Not all states require coccidioidomycosis to be reported as a notifiable condition, and even where it is mandated, electronic reporting systems vary in completeness. Some jurisdictions capture detailed travel histories and occupational exposures, while others do not. The result is a patchwork map in which some apparent gaps in incidence may reflect surveillance artifacts rather than genuine absence of the fungus.
Going forward, several indicators will help clarify how far Coccidioides has spread. First, clusters of pneumonia among workers engaged in soil-disrupting activities-such as solar farm construction, road building, or large-scale agriculture-should trigger targeted testing for coccidioidomycosis, even in states without a prior track record. Second, environmental sampling in areas flagged by climate models as newly suitable could confirm or refute predictions before large outbreaks occur. Third, standardized case-report forms that capture residence, travel, work history, and likely exposure location would allow epidemiologists to distinguish local acquisition from infections picked up elsewhere.
What communities and clinicians can do now
Communities on the leading edge of Valley fever’s expanding range do not have to wait for national statistics to catch up. Public-health departments in at-risk states can begin by educating clinicians about the disease’s symptoms, diagnostic tests, and risk factors, emphasizing that coccidioidomycosis should be in the differential diagnosis for persistent pneumonia, particularly after dust exposure. Outreach to occupational groups-construction crews, farm workers, archaeologists, and outdoor recreation staff-can highlight practical steps like minimizing dust, using respiratory protection during high-risk activities, and promptly seeking care for respiratory illness.
Health systems can bolster their own readiness by integrating prompts into electronic health records that suggest fungal testing when patients present with compatible symptoms and a history of dust exposure in areas with documented or suspected Coccidioides presence. Laboratories can ensure they have validated serologic and, where appropriate, molecular assays available, and that positive results are automatically reported to state health departments.
At the policy level, states that have not yet made Valley fever reportable can consider adding it to their notifiable-condition lists, following the example of jurisdictions that already track the disease. Consistent reporting would not only improve local situational awareness but also feed into regional and national analyses that guide resource allocation, clinical training, and research priorities.
Ultimately, Coccidioides is unlikely to remain confined to its historical desert strongholds. As climate conditions shift and people continue to build, farm, and recreate in newly suitable landscapes, more communities will encounter this long-overlooked pathogen. Recognizing that reality early-by strengthening surveillance, investing in environmental studies, and preparing clinicians to spot the disease-offers the best chance to blunt the health impact of Valley fever as its geographic footprint grows.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
