‘Disease X’ Is a Thought Experiment, Not a Real Disease

Have you heard about the new pandemic, the one caused by a virus that’s 20 times more deadly than COVID, and which has earned the name “Disease X”? If so, heave you also heard that it’s actually just part of a thought experiment, and not a real disease? If you only got half the message, I’ll explain what’s going on. 

Now, most mainstream reporting on Disease X has correctly called out that it is a hypothetical threat, and that world leaders are meeting simply to discuss what they would do if they knew another deadly pandemic were coming. But on social media, the context has been stripped out, leaving behind fear-mongering posts implying Disease X is already here. 

Disease X is the WHO’s term for a “what if”

Never the best at public health messaging, the World Health Organization includes Disease X on its list of priority diseases. (COVID, Ebola, and Zika are some others.) However, it appears in quotation marks, and with an asterisk that directs readers to this note: 

Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease. The R&D Blueprint explicitly seeks to enable early cross-cutting R&D preparedness that is also relevant for an unknown “Disease X”.

In other words, the WHO is saying that they prioritize research that is aimed at their eight top-priority diseases, and research that could help the world manage yet-unknown future pandemics.

In short, the international public health community uses “Disease X” as shorthand for “what if there’s another, worse pandemic?” So when world leaders gathered at Davos to discuss Disease X during yesterday’s World Economic Forum, they were discussing pandemic preparedness. Not anything to do with a specific, known disease.

People are talking about Disease X as if it’s real (it isn’t)

The term “Disease X” was introduced in 2018—before COVID—and it has even been argued that COVID should be considered the first actual Disease X. Certainly if world leaders had paid more attention to Disease X preparedness, we might have responded better to the outbreak of a real-world pandemic. 

But why call it Disease X instead of saying “another pandemic”? Putting a name to something can make it seem more real. As a thought experiment, we can give it properties like “20 times more deadly than COVID” or “expected to be a zoonosis” (that is, a pathogen that jumps to humans from animals). But that doesn’t mean we know of a specific virus that has those properties.

In other words, giving it a name helps to set up a scenario to discuss. World leaders meet to discuss how their governments could battle Disease X in the same way my teenage son and his friends meet to discuss how a rogue, a wizard, and a cleric could battle a dragon. That doesn’t mean that if I overhear them, I’m going to go on TikTok and tell everybody a dragon is coming. 

But that’s exactly what’s happening right now. I logged on to TikTok this morning to hear a man announcing “breaking news that the next pandemic is already on the way,” with a Disease X headline on screen. (He then goes on to share headlines about Nipah virus, which is real, but has also been on the WHO priority list for the past five years—it’s not Disease X.)

In another video, an astrologer tells us that Ketu’s transit through Virgo will cause “new health concerns” this year; the voiceover doesn’t mention a specific disease or scenario, but there are three different Disease X headlines on screen.

And in yet another clip, Bill Gates says (with what appears to be a nervous smirk) that we’ll “have to prepare for the next” pandemic and that it “will get attention this time.” This is a clip that has been circulating among COVID-conspiracy circles since 2020, but now it’s being shared with a caption implying that Gates is the person behind Disease X. As if Disease X even existed. Which again, it does not.

There’s always another pandemic on the way

This may surprise people who don’t hang out with public health or infectious disease experts, but those experts are always talking about the next pandemic. In the early 2000s, my biology professors loved to point out how often flu pandemics come around, and how there hadn’t been a big one in a while, which meant we were due. 

Judging by how COVID caught the governments of the world off guard, it’s more than reasonable to try to do better next time. A 2024 discussion of Disease X might seem a little more ominous than the 2018 discussions, but it’s the same idea. Nature has a way of coming up with horrific new diseases, whether they’re biggies like HIV in the 1980s, or flashes-in-the-pan like SARS in 2003. Will there be another one like COVID? Probably, someday. So instead of fear-mongering, let’s hope those Disease X discussions really do result in better preparedness.

Image Credit: Chinnapong