My Feelings on the Seriousness of Pandemic Risk

Note: When I try to imagine the rest of my lifetime, I feel pretty optimistic. It’s not that I believe that poverty will magically go away or that people aren’t already feeling and won’t continue to feel some of the impacts of climate change. But I do generally speculate that we won’t see a huge pandemic, nuclear war or similar humanity-devastating outcome.

Even though such risks seem unlikely, I have generally felt that they are still worth mitigating given their seriousness if they do happen. I think this explains my interest in the area, which has driven me to work on a couple projects in biosecurity and pandemic preparedness in my PhD. This post lays out lines of reasoning that have influenced my changing feelings about the seriousness of pandemics.

I first learned about pandemic risk from the Open Philanthropy Project (OPP). According to OPP, “[t]he worst flu pandemic in the past century was the ‘Spanish’ flu epidemic of 1918, which is believed to have been responsible for about 50 million deaths,” or 3-5 percent of the world population at the time [0]. The academic biosecurity community [1] in general fears that modern pandemics have the potential to kill even larger percentages: increased travel and other factors potentially augment the risk, while modern medicine and public health knowledge potentially decrease the risk.

How serious is pandemic risk, versus the 30-40 million people who die each year of non-communicable diseases [2], or climate change, or poverty and improved economic well-being (e.g. housing prices)?

tl;dr: At least 2 historical pandemics killed > 3% of the global population within a few years; extrapolating this gives a death toll of > 210 million people today, which in rate terms is an order of magnitude less than that of non-communicable diseases. When considering modern factors that increase pandemic risk (see Red Note), along with the suddenness of pandemics and several scenarios that are worse than historical ones, pandemic risk seems as or more serious to me than suffering from non-communicable diseases.

(Note 1: Comparing pandemic risk and non-communicable diseases does not make me feel, “Oh, non-communicable diseases aren’t that bad.” Like many, I have had family members die and/or suffer from such diseases. This comparison makes me feel, “Wow, surprisingly this problem feels as or more serious than one I already feel is incredibly serious; I should seriously consider working on it.”)

(Note 2: I recommend the 106-minute movie _Contagion_ and, if you have more time, Laurie Garrett’s book _The Coming Plague_ for vivid (and realistic) depictions of pandemics that go beyond the mainly quantitative arguments below. For more background on the specific pandemic threats that could lead to different numbers of deaths including the ones below, as well as actions that can be taken to mitigate such threats, I recommend the 80000 Hours’ podcasts and OPP cause report [3].)

My feelings about seriousness of pandemic risk

1. I first imagined a scenario in which Spanish flu today kills the same percentage of the world population as it did in 1918. That’s 210-350 million deaths (3-5% of the world population) [4]. The Institute of Disease Modeling performed simulations of a modern Spanish flu (presumably accounting for modern factors like increased air travel and more advanced medicine); this 15-second simulation predicted 33 million deaths in the first 6 months:

This IDM number seems significantly lower than the 3-5% extrapolation. Using the 3-5% extrapolation or the IDM results, one modern Spanish flu would kill as many people as non-communicable diseases do in about 5-8 years or 1 year, respectively. If such a Spanish flu happens once or even twice in my lifetime, then in relative terms, the impact is an order of magnitude smaller than that of non-communicable diseases. I dislike engaging in such speculative estimates, but I see no other way to get an intuitive grasp of how serious the problem is. These estimates made me feel the problem is still extremely serious, but less relatively serious than I had initially thought.

2. At this point, I was surprised and asked why I had previously felt so sure that pandemic risk was as or more serious than non-communicable diseases. I then realized that my comparison of total numbers between the two problems missed part of the picture:

  • Many factors increase pandemic risk and magnitudes in the future [5].
  • The worst past pandemic is not a worst case bound on future pandemics, even if such factors don’t end up increasing pandemic risk. I can’t just hope that the worst or average case death toll for a future pandemic is the Spanish flu number (3-5% of world population) or even the Black Death number (until I know more about how these numbers were estimated, I’m not going to put much faith in them, but Wikipedia [6] estimates 16-23% of the world population). Pandemics seem like forest fires in their potential to scale unpredictably and uncontrollably beyond what one might expect [7]: infectious agents self-replicate just like fires, with billions of proximate humans constituting the firewood.
  • Pandemics unpredictably kill a bunch of people at once; this seems worse than something that kills the same number at a slow, steady rate. I mean “worse” in the sense of denting humanity’s trajectory, by unpredictably killing many people of child-bearing age in a short timeframe [8]. In the case of Black Death, “[i]t took 200 years for the world population to recover to its previous level.” [9] In contrast, many of the non-communicable diseases are diseases of old age; they seem to kill no more than a fixed percentage of the world population in predictable ways. This is not captured in comparison of raw numbers.

3. These arguments make me feel again that pandemic risk is extremely serious, at least on par with the suffering caused by non-communicable diseases.

My attitude towards personally working to mitigate pandemic risk

Guided by my interest, I try to pick what to work on based on the seriousness of the problem, how many people are already working on the problem, whether I can actually contribute to the problem and other hard-to-name factors called “personal fit.” The above post only addresses the first factor. At this point, I remain reasonably interested in working to mitigate pandemic risk, as well as other biosecurity risks.


0. Bill Gates paints the picture of a pandemic here:

1. From my current understanding, the academic biosecurity community includes people at the Johns Hopkins Center for Health Security, the Nuclear Threat Initiative, the Open Philanthropy Project and quite a few other institutions. See for a full list.

2. This was generated from






3. See (“When we talk about biosecurity and pandemic preparedness… something even scarier”),, and

4. I don’t know about how the Spanish flu or Black Death death toll estimates are made, so I take them with a grain of salt. However, to take pandemic risk seriously, I don’t require the numbers to be that exact, given that such large numbers are plausible to me based on the exponential nature of pandemics and the huge variance in modern pandemic death tolls, and especially given multiple instances of global pandemics in history.

5. I think there are many factors; ask me if you’re interested. As mentioned before, there are also factors that potentially decrease modern pandemic risk, such as advanced medicine and public health knowledge. I won’t delve into it here, but my feeling is that factors increasing risk outweigh those decreasing it.

6. “In total, the plague may have reduced the world population from an estimated 450 million to 350–375 million in the 14th century.” 75-100 million / 450 million = 16.67-22.22%.

7. I first heard the pandemic-forest fire analogy from Marc Lipsitch.

8. It’s true that flu usually kills the extremely young or old, not those of child-bearing age. I would guess this is due the stronger immunity of young adults and middle-aged people. However, Spanish flu is a notable exception.