Fields, Fires, and Fungi: Valley Fever in the Changing Environment

BY LOLYN TEJEDA LEMUS

A cough can mean anything: a cold, a sore throat, a reflex after a perhaps over-eager sip of water. But as winds pick up earthy remnants of recent harvests, how certain can you be that a cough is benign and not a sign of something treacherous beneath your feet.  Therein lies the unease and concern surrounding Valley fever––illness brought upon by breathing in the wrong soils. Anxieties are heightened in the arid fields of California for the farm workers who cultivate them and the firefighters who preserve them. Yet, a once regionally confined disease, Valley fever is reaching new distances, spreading its endemic risk potential as worsened by climate change. What is Valley fever and how can we stop its spread before it’s too late? 

“Valley fever” (Vf), clinically known as coccidioidomycosis, is a respiratory infection characterized by flu-like symptoms including cough, fever, fatigue, headaches, and muscle/joint aches.^1,2 Despite its benign onset, coccidioidomycosis can spread, worsening symptoms. Patients can develop pneumonia, bronchitis and, if left untreated, Vf can disseminate, causing skin lesions, meningitis or even death.^1,3  Once dissemination has occurred, a patient may require anti-fungal therapies for the rest of their life.⁴ This makes early diagnosis vital in the treatment of Vf. However, due to the difficulty of diagnosis,^5,6 prevention is paramount in Vf management. 

The key to prevention is understanding how and where Vf occurs. Vf is contracted through the inhalation of Coccidioides spp.––a parasitic fungus which inhabits topsoil. The fungus is endemic to the Americas, favoring regions with hot climates and arid soils.^7,8 In the United States, Vf incidences most notably occur in Arizona and California.⁹ Alarmingly, climate warming presents a troubling complication on global soil characteristics––enlarging the area this pathogenic fungus thrives. In just two decades, Vf in the US have spread rampant as far as Colorado, New Mexico, and Washington,^9,10 coinciding with reports of increasing soil aridity and hotter climates.^11,12,13 Exacerbated soil conditions are making the risk of Vf an ever more pressing consideration for locals and travelers, alike.  

Currently, the CDC regards Vf as a relatively rare disease, affecting on average 20,000 people per year in the United States.¹⁰ Contraction rates increase with the quantity of pathogenic material inhaled, dependent on fungal growth and aerosolization of particles.¹⁴ Face coverings, even cloth wrappings, show a significant reduction in disease incidence.¹⁴ However, as climate change alters soil environments, the fungus becomes less confined to its niche, spreading its clinical pathologies. Environmental events are the most correlated factors with spikes in Vf incidence; earthquakes and wildfires disrupt soils, increasing the amount of airborne fungal particles, and wind transports this material across longer distances.^15,16,17,18 Now, more so than ever, exposure to Vf-ridden soils is almost inevitable for many communities. Already, some groups show immense vulnerability.

Agriculture faces the greatest risk for Vf. Seven California counties––Fresno, Kern, Kings, Madera, Merced, Tulare, and San Luis Obispo––account for over 52% of the state’s Vf cases in 2023, despite amounting less than 9% of the population.^19,20,21 Migrant farm workers, especially, are susceptible to illness as their work quite literally enshrouds them in clouds of soil dust. Root vegetables, in particular, provide the highest reported risk for Vf incidence among harvesters.²²  Over 800,000 migrant and seasonal workers are employed in California agriculture.²³ Providing nearly two-thirds of the nation’s fruits and vegetables, these unsung heroes withstand physically demanding work and endure the brunt of climate change’s effects. As a result, protections against Vf become secondary to an ability to carry out daily responsibilities.

The effectiveness of masks against Vf cannot be overstated. N95 masks show up to 99% reductions of Vf risk; even bandanas are suggestively recommended over having no mask at all.¹⁴ Yet, many farm workers do not wear masks while they work. A study conducted by the University of California (UC) Davis and UC Merced surveyed California Hispanic farm workers to glean insights on common knowledge and behaviors of Vf. They found that while most workers understand that facial coverings are a vital component to disease prevention, most men rarely wear masks during work.²⁴ This troubling habit seems counterintuitive, but the summer sun may shed light on why this occurs. With concerns for smoke inhalation, a study at UC Davis found that heat-discomfort and chafing make mask wearing undesirable in the field.²⁵ From 2005 to 2021, 94% of fatal heat-related illness reports were farm workers.²⁶ As these worries rise with increasing global temperatures, where does that leave farm workers with Vf prevention? 

Climate change is rapidly altering the face of agriculture from heat waves to soil properties. As droughts are more prevalent than ever, California farmers have had to adapt to these water shortages. One method of decreasing a farm’s water demands is fallowing land (i.e. leaving a portion of land unplanted). With the onset of the 2021 California drought, however, the Public Policy Institute of California estimates that over 395,000 acres of additional land has been idled.²⁷ This raises some concerns for Vf risk potential. California soils are becoming more arid as average temperature minimums continually increase.^12,11 This, in turn, makes soil aerosolization far more likely. Moreover, as idle lands have no crops, the lack of plant roots decreases the soil’s water carrying capacity, exacerbating this moisture deficit.²⁸ With one inopportune harvest just downwind of these fallowed lands, migrant farm workers must evade the hazards from beneath their feet and in the surrounding air. 

Farmers are not alone in this fear, however, as more research reveals that when there’s smoke, there is Valley fever. 

Firefighters, like farm workers, are exposed to airborne soils. Vegetation removal and frequent soil disturbance provides occupational risk of Vf to firefighters.²⁸ In July 2021, the California Department of Public Health received reports of two crews of firefighters with multiple cases of Vf, some requiring hospitalization.²⁹ Called to a wildfire outbreak near the California Tehachapi Mountains, the firefighters recounted “mopping up” the fire––a duty which involves digging and moving soils––without respirators.²⁹ Despite knowing the dangers of working with airborne particles, firefighters raise similar concerns to farm workers wearing face masks in hot conditions. Furthermore, the feasibility of respirator use for firefighters becomes worrisome in considerations of flammability and compatibility with other equipment.²⁹ Similar to farm workers, the firefighter’s job, without foolproof means of protection, places them at great risk. However, this occupational hazard poses an even greater concern for a subset of this group: inmate firefighters.

Incarcerated individuals are among the most susceptible to Vf incidence than any other group in California. Two California Department of Corrections and Rehabilitation men’s prisons––located in highly endemic regions––showed rates of Vf 75-times greater than prisons located elsewhere.³⁰ For those who are also inmate firefighters, the exposure to airborne fungal particles increases many-fold. In August 2017, a cluster of Vf cases were reported in a single group of inmate wildland firefighters.³¹  A survey of the inmate firefighters unveiled more troubling concerns. Only two of the 112 firefighters surveyed reported being trained for Vf prevention and zero firefighters wore face masks despite working in dusty conditions.³¹ This year, over 1,000 inmate firefighters were employed to combat the Los Angeles fires.³² For a fraction of the pay, it is clear these individuals are fighting more than just fire; they are evading disease.  

“Fire season” poses more concern than just its immediate danger. Wildfires are among the most notorious natural disasters which afflict California, becoming more frequent and severe each year.^33,34 Calling firefighters to action from across the state, wildfire outbreaks can spark a surge in Vf reports in the surrounding area. But direct exposure to airborne soils in the line of fire is not the only way to contract Vf. A retrospective study found that in the month following wildfire smoke exposure, hospitalization rates in the surrounding area due to Vf increased by 20%.¹⁷ More research is necessary to understand the mechanisms of transport, but preliminary studies demonstrate smoke’s potential to carry microbes long distances, including the fungal particles of Vf.³⁵ As fire frequency is estimated to increase, so does the exposure potential for pollutants and (possibly) pathogens in emissions.³⁴ This is restricted to neither careers which have identified Vf as an occupational hazard nor populations residing in the fungi’s endemic region. The looming danger––and reason why Vf reports have reached well outside of California––is for all residing in and around high disease-incidence, especially pregnant women, people over the age of 60, and immunocompromised individuals.³⁶ As climate change worsens, this danger zone widens. Though worrisome, the issue is not unsolvable. So, what can be done?

For starters, improving awareness and knowledge of Vf is a step in the right direction. While three-quarters of Hispanic farm workers report being aware of residing in in areas of high-incidence, a survey for the 2016-2017 California Behavioral Risk Factor Surveillance System reported only 25% of participants were aware of their increased risk of exposure.^24,37 A similar lack of knowledge is demonstrated amongst firefighters³¹ and the general population.^24,38 Improving awareness on Valley fever––its region of endemicity, its pathogenesis, and its clinical symptoms––will prompt more patients to ask their doctors to be tested for Vf. Moreover, this will catalyze the implementation of prevention methods in daily practices, like mask usage. That said, the hazards that face coverings and respirators pose farm workers and firefighters, respectively, cannot be ignored. Alternative prevention methods like wetting soil and frequent tilling offer the possibility for containment of particles and disruption of fungal growth.³⁹ These methods provide protections against Vf that reduce aerosolized soils and, by extension, pathogen exposure. However, preventions are only half the battle, thwarting only a danger on the individual scale. What about those at the fungi’s endemic periphery? How can the spread of Vf be impeded?

Climate change poses a particular danger towards populations just outside of the endemic region of Vf. Favoring arid and high-temperature conditions, Vf fungi thrive in the climate of California’s elevating temperature minimums.^12,11 With a strong and sustained wind event, the fungi can become airborne and can travel hundreds of miles outside of the endemic zone.¹⁵ That is to say, risk of Vf reaches far beyond its endemic zone. If climate change continues to increase soil temperatures and decrease soil moisture, Vf will continue to spread, afflicting populations that have hitherto been unaffected. Although not a panacea, certain practices can be implemented to help combat climate change and the spread of Valley fever. From the reduction of carbon-gas emissions to the potential of biochar carbon sequestration, steps can be taken to reduce the toll of greenhouse effects.^40,41 Further research should also be conducted to mitigate fungal growth in soils directly. Preventative practices are key to maintaining individual health. However, addressing climate change is necessary to resolve the impending spread of Vf and detriment of already afflicted groups. 

Valley fever will never be understood without considerations of environmental science. Contracted from a soil-dwelling pathogenic fungus, Vf necessitates the implementation of preventative measures to preserve the health and safety of those residing in endemic regions, especially farm workers and firefighters. The number of occupational hazards farm workers and firefighters must face is already innumerable. By raising awareness on the disease, people can find the treatment they need before it’s too late. But, as aridity spreads like a rash on the western face of the US, the detriment Vf poses on public health is brought further and further into the limelight. Although an uncommon illness, the spread of Vf into once-unaffected regions is not an isolated occurrence. Vf evidences a much larger trend in public health, one that largely concerns environmental science. Its spread signifies the greater vulnerability we face if we remain complacent in the fight against climate change.

Lolyn Tejeda Lemus is a recent graduate of Jonathan Edwards College.

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