You need to start taking airborne fungal outbreaks seriously

Vox

26-02-2025

As our planet gets increasingly warmer, we're seeing in real-time the myriad of ways our climate is changing: unbearably hot summers, extreme cold snaps, and more dangerous natural disasters. And when our environment changes, so do we — especially in regards to our health.
Valley fever, a fungal disease that invades our lungs, is one of these not-so-obvious public health concerns. The fungus, which is typically present in the Western United States, is projected to spread to new frontiers across the country, my former colleague Keren Landman reported back in 2023.
We knew then that climate change had played some kind of role. Now, more evidence is coming in about this looming public health threat. Last week, The Journal of the American Medical Association ( JAMA ) published a brief aimed at practicing doctors that drove home just how neglected Valley fever — and by proxy, other diseases like it — can be.
According to the brief, California's Department of Public Health recorded over 9,000 cases of Valley fever in 2023, the highest number of recorded cases on record. That same year, California had multiple storms that drenched the state over the course of a few weeks, after a long period of drought starting in 2020. These conditions — long spells of extremely dry weather followed by intense rain — are just right for Valley fever growth and in turn, infections.
The earliest recorded case of Valley fever dates back to the 1890s. For some people, it's totally asymptomatic. But for others, Valley fever can cause symptoms for weeks or months. And then there's the unlucky few whose infection travels outside of the lungs and into the skin, bones, or brain. Severe cases can be life-changing and even fatal.
According to the brief, Valley fever is pretty significantly underdiagnosed — cases may be up to 10 to 18 times higher than the 10,000 to 20,000 cases reported to the CDC annually. Doctors can miss the signs because the symptoms are similar to other respiratory infections: a cough, fever, feeling tired. That ends up delaying treatment for people who end up really needing it.
'There's some people who get really debilitating forms of this disease, where they are on lifelong treatment. They're in and out of the hospital,' said Pamela Lee, an infectious disease physician at Harbor-UCLA Medical Center and one of the authors of the Valley fever brief. 'And one of the things that I worry about is that sometimes people can almost dismiss this disease.'
Climate change is doing more than just making the days hotter or the weather more extreme. It's shifting how preexisting diseases grow and spread — and increasing the burden on often underprepared communities and health institutions. In addition to Valley fever, we're seeing the exacerbation of harmful algal blooms in places like Florida, the spread of malaria- and dengue-carrying mosquitos in non-endemic areas, and hot days exacerbating already prevalent air pollution inequities in Eastern North Carolina.
Despite how increasingly important this intersection between climate change, disease, and health is becoming, there still are challenges — from the scientific to the political — in doing research that unravels these connections. It's not enough for these new risks to be observed. Quantifying the health impacts of neglected diseases and public health outbreaks that are attributable to climate change is critical to understanding how we adapt, and the scale of the imminent risks that lie ahead.
'I think this is another one of those kinds of things that we need to be thinking about as a prevalent and chronic threat that's going to be riskier for some people more than others — but that no one is totally free from risk,' said Daniel Swain, co-author of the brief and Future Perfect 50 honoree.
Coccidioides, the fungus that causes Valley fever, lives in the soil of arid states. Once the fungal spores in the ground are dispersed into the air, often by the wind or human activities like construction projects and farming, it takes inhaling just a few spores to be infected.
But what's driving the growth in Coccidioides is an era of weather whiplash: rapid swing from one weather extreme to another. In the case of the fungal spores that cause Valley fever, shifts from extremely dry to extremely wet weather are the perfect conditions for Coccidioides to thrive.
'It's actually not just enough for it to be dry all the time, or the fungus would never actually grow. It's also not enough for it to be wet all the time, or it would never aerosolize,' says Swain. 'It actually does require that there be these transitions between wet and dry states in some form.'
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People with jobs that disrupt soil in Valley fever hot spots can have a higher risk of getting infected, such as construction workers and agricultural workers. These workers also tend to have challenges in accessing healthcare, leaving them susceptible to forgoing a diagnosis and, if necessary, treatment.
'These are the types of patients that I see all the time where just going to the doctor takes away an entire day of income for them, and they can't afford that,' Lee told Vox.
But as our climate changes, researchers expect to see more than just a rise in the number of cases — they predict that infections will jump beyond its current geographical borders, too. Valley fever will likely spread to Idaho, Wyoming, Montana, Nebraska, and the Dakotas in the next 75 years. It's a public health issue that's crossing borders where it hasn't before. 'This is an example of something that we were 100 percent sure has been around for a long time, but has a much greater public health burden that it used to and is probably expanding to new regions,' Swain said.
The spread of Valley fever imposes a financial cost, too. One study found that the economic burden associated with Valley fever in response to climate change could be $18.5 billion a year by 2090, from direct costs like hospitalization to indirect costs like loss of income. Yes, tens of billions of dollars a year from one disease alone.
Valley fever is just one, singular disease. Now, imagine the total human and economic toll of a heating planet that exacerbates the spread of other illnesses and public health crises. It's clearly a massive crisis — but one that researchers are still trying to quantify.
It's clear that our changing climate is having some sort of impact on human health. But exactly how climate change is playing a role, and to what extent it's driving infections and deaths, is still being figured out by researchers.
Colin Carlson, an assistant professor of epidemiology at Yale University School of Public Health, says there are diseases that researchers know are climate-sensitive, but are still missing observational epidemiological studies to show more concretely how climate change is attributable to the burden of these diseases.
'There is a huge amount of literature about climate and health,' Carlson told Vox. 'There's not as much literature about climate change and health.'
Carlson maintains a database of studies that compiles this specific literature called the Health Attribution Library. The papers in this database quantify the human health impacts (like deaths, injuries, or infections) of human-caused climate change. Dengue, malaria, heat deaths, and fire-related deaths from air pollution have attribution studies, while other diseases like cholera, yellow fever, and West Nile virus haven't. Beyond infectious diseases, public health concerns like spikes in depression and anxiety may also be attributable to climate change.
'We know that there is a huge, strong relationship between temperature and suicides, but we don't have a global estimate of how many temperature-attributable suicides there are, or how many are attributable to climate change,' says Carlson.
Part of the issue of doing health impact attributional studies is that, ultimately, it's difficult to do. One big challenge that researchers run into is lacking long-term, large-scale data. Carlson added that his lab did an attribution study on malaria because there was data to work with.
Of course, there are challenges beyond the scientific. The Trump administration's latest policies and actions don't bode well for the next four years of progress in climate and public health, domestically and abroad.
'I think the intersection of climate change and public health is particularly concerning because both seem to be partisan, ideological targets right now, specifically, individually,' says Swain. 'Together, they pose a huge threat to the health well-being and the economy of the US.'
Though many uncertainties lie ahead in the future of climate and public health research, and in turn, the future of human health, Carlson adds that attributional studies can be a point of progress for the people whose lives will be harmed by climate change.
'These attribution studies are incredibly useful in legal settings, because they can demonstrate that plaintiffs have a basis for their damages,' he said. 'When climate litigation has been successful, it has often been on the back of health.'