I'm sorry, you're not going to die from an AI-engineered supervirus

God save us from economists who think they can competently talk about biology

Opinion writer and economist Noah Smith just dropped an article about AI-designed superviruses. Oh man. I used to think Smith was a person with informed opinions, but reading his take on a topic close to my own expertise makes me question this premise. No worries though. I’m sure I’ll read his takes on inflation tomorrow and nod along. Gell-Mann amnesia is real.

Photo by Jei Lee on Unsplash

The article opens with a fictitious story about a disgruntled teenager in 2029¹ who asks an AI to design some lethal viruses, which he then deploys and ends up killing 90% of the human population.

Immediately following this story, Smith writes: “I have yet to hear an even halfway-convincing argument as to why this scenario is far-fetched.” Pro-tip: When you find yourself writing such a statement about a topic you’re not an expert in, there are only two possibilities: 1. You are not talking to the right people. 2. You are talking to the right people but you’re not listening to what they’re saying. On that note: The article is paywalled. I can’t read beyond the first few introductory paragraphs. I also can’t post comments. All I can do is write on my own blog, making some assumptions about what the article may say. It is possible that every point I’m making here is competently addressed and strongly refuted in Smith’s article. If that’s the case, more power to him, and I’ll stand corrected.

Who am I? Why should you listen to me? Well, for one, unlike Noah Smith, I have actually computationally designed viruses and other biological systems.² Also, my day job involves developing and evaluating AI systems for protein and peptide design. So I know a thing or two about state-of-the-art AI tools in biology and about the challenges of designing and building functional biological systems. I also know a bit of virology.

Computational design of biological systems is unfathomably difficult. Experts who have dedicated their life to this topic routinely hit their head against the wall when nothing they try seems to work. PhD students in 2026 using state-of-the-art AI software are spending months or years trying to design simple peptide binders that inhibit some enzyme or pull down some protein, and the majority of their designs fail, or don’t express, or are toxic.³ But in Smith’s fictitious world a disgruntled teenager with no special training in biology can just solve a problem thousands of times more complicated than designing a peptide binder. The distance between where we are today and where we would have to be for Smith’s story to have any realism is enormous. And then, even if you could design the perfect virus, assembling and distributing it would be a non-trivial task in its own right. You don’t just order a working virus from temu.com. See for example this article by Abi Olvera.

I’m not discounting the possibility that at some point somebody may cause some harm with an AI-designed biological agent. But we need to consider scale. A disgruntled teenager could also get their hands on a fertilizer bomb and blow up a busy shopping mall. No AI needed. So damage on the scale of maybe a couple hundred to a couple thousand people dead, while devastating for the individuals affected, is not an existential threat. The question is whether a much larger attack is possible. Something that would kill millions of people.⁴ I am quite confident this is not something we need to worry about, at least not for another few decades.⁵

Nobody knows how to build a supervirus

Let’s set aside all the issues of whether AI can design viruses, how hard it may be to then build them, and finally to distribute them to unsuspecting victims. Let’s assume all of these issues are solved.⁶ So, you’re armed with your supervirus-generating AI and your rogue lab that will synthesize and weaponize viruses for you. What properties do you want the viruses to have?

“Well, duh,” you say, “I want them to be lethal!” Ok, here you go: Ebola virus, hantavirus, rabies virus. All extremely lethal. And yet, we’re not really that worried about them. At least we don’t think of them as civilization-ending superviruses. Why is that?

Hantavirus doesn’t spread human-to-human.⁷ Don’t inhale infected rat droppings and you won’t get it. Similarly, rabies doesn’t transmit human-to-human, primarily because once people are becoming contagious they are so incapacitated that they’re unlikely to bite you. Now Ebola is different, it is actually quite contagious, but it requires contact with the bodily fluids of an infected person and that contact is easily avoided unless you’re a direct caregiver.

“Ok then,” you may say, “I want them to spread through the air!” That’s fine, plenty of viruses spread easily, but there’s generally a tradeoff between how easy a virus spreads and how lethal it is. For a virus to spread easily, the infected patient needs to shed a lot of viral particles, and this requires a high viral load. But, the patient needs to be able to walk around and function while experiencing a high viral load, otherwise they won’t spread the virus. This generally means the virus is not that deadly. An example of a virus that spreads extremely well is measles virus. The virus can remain suspended in the air for up to two hours. If you enter a room in which two hours prior somebody with measles spent 15 minutes you may you catch the disease. But, measles kills “only” about one in a thousand infected people. It’s incredibly contagious, but it’s not that deadly. It’s really bad though. We’ll get back to it later.

“I got it now,” you may say, “I want viruses that have a long incubation period, during which they can get transmitted, and then later I want the infection to turn really bad and kill the patient.” Ok, fine, such a thing would probably deserve the label “supervirus.”⁸ I’m not sure what the biological mechanism would be though. How do you build this? Viruses with long incubation periods are typically not contagious during the asymptomatic period. The may integrate into the host genome and lay dormant for a while, only to reactivate later (e.g., varicella-zoster virus, the causative agent of chickenpox and shingles). Or they slowly make their way through your nervous system (e.g., rabies virus). The one virus that sort of has the properties we’re looking for is HIV. Extremely long incubation period. Patients can be contagious without showing obvious symptoms. Nearly 100% lethal without treatment. But, not easily transmitted. We commonly see this tradeoff. Viruses that hide in specific compartments of the body for long periods of time will not usually transmit easily. I’m not aware of any virus that has even remotely similar properties to HIV but spreads like a respiratory virus.

In general, there are tradeoffs between how lethal a virus is and how easily it spreads. Consider the common flu (H3N2 influenza) and avian influenza (in particular, H5N1). H3N2 influenza transmits easily person-to-person because it targets a receptor that is located in the upper respiratory tract. H5N1 influenza, by contrast, targets a receptor that is located in the lower lungs. This causes more severe disease but limits spread. Epidemiologists have reasonable concerns about a potential H5N1 pandemic, but to date the tradeoff has held. We have not seen a civilization-ending H5N1 pandemic.

There is simply no good reason to believe that AI will magically be able to work around these fundamental tradeoffs of biology, that it could somehow design a virus with the lethality of H5N1 influenza but the contagiousness of H3N2. The basic science required to build such a thing has not been done. When people believe that AI could figure this out on its own, without first running extensive and expensive basic science experiments, they have left the realm of science and have entered what can only be described as religion. They hold a strong belief not supported by any evidence or causal chain of logic.

The viruses causing the most damage are not what you think they are

As I just said, a virus that first spreads silently throughout the population and then flips a switch and kills everybody is science fiction. It does not exist and will never exist. And among the viruses that do exist, the ones that seem the scariest are not necessarily the ones causing the most damage. For any virus that does or could exist, we have to consider how an outbreak would affect and interact with human behavior.

Consider the spectrum of possible viruses, from mild to highly lethal. On one end you have something like the common cold, which spreads easily and infects millions of people every year. It rarely causes serious illness so people mostly just ignore it and live their regular lives. The total damage caused by the common cold, in terms of morbidity and mortality, is not that large because the infection is rarely lethal. On the other end of the spectrum, you have something like Ebola, with mortality rate up to 90%.⁹ Ebola is a scary virus. It is a killer. Yet the total number of people killed by Ebola is not that high either. Getting infected with Ebola is generally a death sentence, and therefore people take it seriously and do their best to avoid transmission. Ebola will never turn into a world-wide pandemic. If Ebola prevalence kept rising, at some point people would simply isolate, stop interacting with the world, and wait it out. The viruses causing the most damage are not found on either end of the lethality spectrum, they live in the middle.

There is a Goldilocks zone of lethality for a pandemic virus that will cause maximum mortality, and it’s a level of lethality that is much lower than you may think.¹⁰ In fact, I think COVID was close to ideal in terms of a virus causing global morbidity and mortality. It caused sufficiently severe infections that many millions globally died, and yet its infections were also often sufficiently mild that people could just dismiss the virus and pretend it wasn’t an issue, thus contributing to further viral spread. Notably, COVID also had the property of asymptomatic transmission, where some people spread the virus without themselves feeling particularly sick or showing any symptoms. It was near perfect as a pandemic supervirus.¹¹

So, if you’re worried about AI-designed superviruses, think COVID, not Ebola. And if you’re now a little less worried, maybe you understand where I’m coming from.¹² Yes, COVID was bad. But it did not end civilization. We’re still here. At least those of us who survived. If somebody actually designed a virus with AI, which I still maintain is virtually impossible, I doubt they could do more damage than COVID did.

The risk from nature is still worse

What really bothers me about these stories about how AI will design killer viruses is that they are pure fear mongering, and more importantly they divert attention from the things that matter. There are deadly viruses all around us, and viruses routinely jump from animals to humans and cause severe outbreaks. This is a real, documented risk. This is the risk we should worry about. This is the risk we should prepare for. But instead, we worry about fictitious AI-designed viruses while ignoring the real viruses that stare us in the face.

Let’s go back to measles. It is bad. Really bad. If somebody gave themselves the goal of designing a supervirus and came up with something like the measles we’d probably call that a success. Measles is incredibly contagious. On average, every infected person infects over ten other people. Around 10-20% of measles cases result in hospitalization, and about one in a thousand results in death. And if you survive the measles, you may experience permanent vision loss, hearing loss, brain damage, intellectual disability, or a destroyed immune system. If you’re really unlucky, 10–20 years after your measles infection you develop subacute sclerosing panencephalitis, which is an awful, progressive brain disease that slowly turns your brain into mush and eventually kills you.

Now here’s a real risk involving measles that I sometimes worry about. What if the measles virus experienced a set of immune escape mutations where suddenly existing vaccines no longer work? If this happened the consequences would be horrifying. We’d have an immediate, world-wide measles epidemic long before we could develop and roll out a new vaccine. What’s the likelihood this will happen? Informed estimates are that it is low. But realistically speaking, even if the likelihood is low, it’s probably higher than the likelihood that a disgruntled teenager will design a supervirus with AI. So, something to think about.

More generally, it feels to me like society is currently not particularly concerned about real viruses causing real devastation. There’s a massive Ebola outbreak right now in the Congo. Nobody cares. Measles are surging in the US. Nobody cares. HIV is running rampant in Sub-Saharan Africa. Nobody cares. And for sure nobody cares anymore about COVID. So spare me your concerns about fictitious, AI-generated superviruses.

What protects us from deadly viruses, regardless of their origin, is good public health practices and basic research. Ongoing surveillance to catch emerging pathogens early. Consistent vaccination against known pathogens so they are kept in check. Research into rapid vaccine development and into novel antivirals. Investments into improved indoor air quality and air filtering. Consistent hand washing. But this stuff is boring and doesn’t sell Substack subscriptions. Let’s be real. Fear mongering about AI superviruses is a much better strategy to make money online.

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1. 2029 is just the icing on the cake. That’s three years from today. Make it at least 2049 so I can experience some suspension of disbelief.

2. For example, in 2012, my lab introduced up to 182 mutations at once into bacteriophage T7, demonstrating that we could deliberately reduce T7 virulence in a controlled manner by increasing or decreasing the number of mutations we added. We also showed that we had succeeded with the original design goal of building a virus that would have difficulty adapting to the introduced changes, an important consideration when engineering a virus. You don’t want it to undo your changes the moment it starts replicating. (Our experiment was in the context of vaccine design, where you want to ensure an attenuated virus remains attenuated when injected into patients.)

3. I have written about this issue previously here.

4. And 90% of the population dead, as asserted in Smith’s story, is completely off base. This will never happen.

5. I am willing to concede that the world may look different in 2049. We’ll see.

6. Just to reiterate: They are not.

7. Yes, I know of the Andes strain that has some documented human-to-human transmission.

8. And, to be fair, Smith envisions such a virus. Once you’re operating in the realm of fiction anything goes.

9. The exact mortality rate of Ebola depends on the strain and also on the quality of care available to infected people. It is possible to survive an Ebola infection with modern intensive care. Nevertheless, an Ebola infection is extremely serious and has a high likelihood of resulting in death.

10. See for example this study and also the book Asymptomatic by Joshua Weitz.

11. And just to get this out of the way: No, COVID was not designed in a lab. There is absolutely no evidence for this. We also don’t have the technology to fine-tune a virus so it has just the right characteristics in terms of virulence and contagiousness and asymptomatic spread. COVID was an animal virus that happened to jump the species barrier, just like SARS-CoV-1 and MERS-CoV before it.

12. But maybe you also have to reassess how bad COVID actually was. Remember overflowing morgues in New York City? Yes, that was a thing.