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Colin CarlsonSeptember 25, 2026 at 3:23 PM EDT

David Quammen's essay in The New York Times today closes with this paragraph. It's both a scientific falsehood, and an incredibly dangerous narrative. If you're willing to give me five minutes of your time, I'd like to explain why.

Here's the link to his essay. I'm going to address this in four parts: (1) The basic scientific error a fact-checker should have caught; (2) Incompatibility with existing science; (3) How our new paper challenges other supporting evidence; and (4) The consequences. nytimes.com

1. A basic, and massive, scientific error. David states unambiguously that Ebola outbreaks end with the last human case, and cannot re-emerge without zoonotic spillover. This is categorically false, and has been consequentially false in just the last few years.

In reality, we now also know that persistent viral infection in Ebola survivors is not only a possible source of new outbreaks, but in fact a very serious problem - one that gets worse when we have major outbreaks, such as the 2014 epidemic in West Africa, or the current Bundibugyo virus outbreak. Viral persistence is believed to be the origin of the 2021 re-emergence of Ebola virus in Guinea, five years after the end of the previous outbreak. nature.com

Similarly, one of the two 2020 outbreaks of Ebola in the DRC was a re-emergence from the 2018 outbreak. thelancet.com

I believe this is a deliberate oversimplification, not an accident. I am certain David knows this. I am also relatively astonished the NYT's fact-checkers didn't spot this. But on its merits, it is false to claim the threat of Ebola virus outbreaks will end in the absence of spillover. 2. David claims that spillover cannot happen in the absence of wildlife use or deforestation: "If humans left the reservoir host alone — not hunting it, not capturing it, not eating it, not exporting it live, not disturbing its forest habitat — the virus wouldn’t re-emerge in humans." In reality: 1. Roughly half of historical Ebola outbreaks are linked to wildlife use, while the other half are something of a mystery.

2. Bats frequently roost in human structures, undoubtedly exposing humans to viruses passively - while humans are "leaving them alone." journals.plos.org

These interactions are undoubtedly accelerated by deforestation, but the idea that people have not come into contact with bats for millennia, only for this to change in the last fifty years is, again, an oversimplification. As for the link between deforestation and Ebola, the strongest evidence of this link comes from studies that have tried to make sense of the very small (<50, usually much fewer) number of known outbreaks: nature.com nature.com More on that in a second. There's also this much newer paper, which makes a really interesting (and to me, compelling) argument using viral phylogenetics and landscape history to argue that fragmented landscapes accelerated viral circulation over the last century. esajournals.onlinelibrary.wiley.com

The best way I could summarize the state of the evidence is: there's okay evidence for a long-term process where land use has driven the emergence of Ebola viruses; there's circumstantial evidence that outbreaks start near where deforestation has recently taken place. If humans came into less direct contact with bats and other wildlife, Ebola spillover would probably be more rare. Whether the land use effects are reversible is a more complex story. The drivers are real; the idea that spillover is unnatural, and can only happen in their presence, is embellishment. 3. Our new study further complicates this narrative, showing that in this and many systems, records of outbreak geography primarily tell us where we have surveillance infrastructure - and, when you take those signals out, the land use *change* story often drops out. bsky.app

Colin Carlson09/23/26

What's behind this tidal wave of epidemics? In the largest study ever conducted on emerging infectious diseases, we show that the popular explanation - "our relationship with nature is out of balance" - doesn't hold up. Out now in Nature, after half a decade of work: nature.com

The anthropogenic fingerprint on emerging infectious diseases - Nature

www.nature.com

I am emphasizing change here because land use and land use change are a meaningful distinction: we find that people get sick in fragmented landscapes where they live near forests; it's less common that we find people get sick where forests are being cut down to use the land for something else. This is true for Ebola, where we find only one significant association with forests - and not deforestation.

This doesn't disprove a role for deforestation, but it suggests that current data don't contain a detectable signal. Other studies mine these same data harder for that signal, and if you squint, they find it - but they also don't control for the bias issues we do. Basically: it's really hard to know "It's hard to know" isn't the same thing as "deforestation doesn't drive Ebola." But what David is presenting here - that if we stopped cutting down rainforest, we'd stop having Ebola outbreaks - is a matter of his personal narrative he's crafted across his career, not scientific evidence. In addition, one of the most important open questions in our field is whether these changes are reversible. I'm persuaded that land use changes going back to the 1940s may have changed viral dynamics in wildlife - but that might just be how things are now, even if we stop deforesting. David is aware of all of this nuance as well as our specific paper; the way that I know this is that I've spoken to him multiple times over the years, as well as to the subset of scientists he's interested in listening to, who are primarily interested in evidence that supports his worldview in turn. The simple fact is that David Quammen is a storyteller, not a scientist, and his approach to evidence is based around what supports his favored story. I am not sure what words do or don't apply to such a person; is he an expert, or an advocate? 4. Based on my expert understanding, here is how I would summarize what I think the science says: human pressure on wildlife populations has accelerated Ebola virus spillover, and an appropriate policy strategy accepts that outbreaks are always possible, and emphasizes both prevention and response. When I confront pandemic prevention advocates they often claim this has always been their point. I suspect David would say the same. But fundamentally, that's not what he's written here, and if there's anywhere you have to choose your words carefully and be held to them, it's the New York Times.

This narrative is part of a broader one that places the blame for pandemic risk on the Global South, and demands that they think less about how colonialism has entrenched poverty and denied them vaccines, and think more about how to responsibly manage their rainforests and wildlife populations. I am not going to spend another twenty posts discussing how this is an exploitive, neo-colonial policy frame shamelessly used by conservationists to exploit global health for their own objectives, because I've been writing about it my entire fucking career. carlsonlab.bio

My entire fucking career. thelancet.com

No, really, my entire fucking career. nature.com

I cannot ignore this now, as I have never been able to ignore it before, because getting the science wrong leads to the wrong policy frame: if you believe that you can prevent every outbreak simply by living in harmony with nature, there is no reason to invest in preparedness or health systems. So let me set the record straight, using the language of climate change and extreme weather, because I think it's the most intuitive way to understand why David is wrong, and how policymakers *should* think about this. Think of spillover as extreme weather, and think of the pressure we're putting on ecosystems as climate change. Spillover is naturally occurring as a phenomenon, but the contemporary (post-1950) spike in spillover is probably mostly, if not entirely, due to human pressure on ecosystems.

The only way to reverse the trend is to mitigate pressure on ecosystems, but (1) futures where we have pre-1950-like impacts on ecosystems are probably not attainable and (2) some changes, like the effects of a century of land use change on Ebola, may be irreversible. medrxiv.org

I hope it is obvious I am not some sort of science denier here: there are very few labs who have quantified the role of global change in viral spillover more than mine. What I take issue with is the policy frame that, in the absence of climate change, we would never have to worry about hurricanes. It's time to stop letting a small number of white American journalists who write airport books about scary diseases set the policy frame for pandemics. And it's unbelievably galling to do it - and this is always how it happens - in the middle of an ongoing Ebola virus epidemic. /fin (unless I think of something else that pisses me off) Thought of something else. This is one of the last areas of environmentalism that really traffics in the idea that stupid Africans don’t know how to manage their rainforests / disgusting Africans and Asians just can’t help but eat wildlife when alternative proteins are right there. Putting aside all the ways the quiet racist part is said aloud, it’s also a bad analysis of power. The truth is: we’re paying to cut down the rainforest in Ebola hotspots - even U.S. universities thelancet.com

Replacing wildlife protein with livestock production would also require substantial land conversion, leading to more extinctions - **and presumably more spillover** cell.com

Fundamentally, this entire worldview is just mad that Africans have to exist in a place that should be undisturbed and unpopulated rainforest. Turn it into a nature preserve. That’s the contemptible premise

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