I’ve been thinking a lot about COVID-19 and what I can do about it. I’ve been following the news and the research, and I’ve been talking to everyone I know who is following the science. Amid the bedlam, it is clear that in the countries where the disease is still incubating, such as the United States, the average informed person still doesn’t comprehend the gravity of the COVID-19 pandemic. I’m not talking about the US president. Normal, informed people think this is just like the flu, or maybe just a common cold. This perception must change.

We still don’t know what fraction of the US or world population will end up contracting COVID-19 during the pandemic. A lot of numbers are thrown around and estimates are not stable.

But this morning German chancellor Angela Merkel, a leader who makes policy decisions based on science, warned that 70% of the German population could be infected. At this point it is fairly safe to say that Germany is doing at worst an average job of managing the pandemic. Countries such as South Korea and Singapore are clearly doing better than average. All signs point to the US ultimately being significantly worse than average. So, Merkel’s 70% is a number we should view as a relatively safe, but optimistic estimate of the fraction of people on the planet who will contract COVID-19, if they are so lucky to live in advanced countries that do an average job of containing the pandemic. If you do the math, that’s certainly a lot of people, and presents a potentially massive and tragic loss of life. However, there’s a much smaller number that I think will frighten people more.

Let me asking two questions: Have you ever known anyone who died to Influenza? Also, have you ever been to a large wedding? Say 150 people? Hold on to your answers for a minute.

To understand COVID-19, another number that we need to know is how many people, who once infected, eventually succumb to the disease. This is technically called the CFR, for Case Fatality Rate. Estimates for this vary substantially: The WHO stated last week that the CFR could be as high as 3.4%. However, recent evidence from South Korea and Singapore, two countries that seem to be effectively battling the disease, suggest that the CFR may be closer to 1%.

If we use Merkel’s 70% and a conservative 1% estimate for CFR, that means that we can reasonably expect, from what we know today, that roughly 0.7% of the population of developed nations could die to the illness during the pandemic. 0.7% = 0.007 = 1/149.

Now I want to ask another question: How many people do you know? With how many people are you able to maintain stable social relationships? I don’t know you at all but I’ll tell you that the answer is about 150. Anthropologist Robin Dunbar studied this topic in the context of primate relationships. He found that there is a positive correlation between the size of the primate brain and the average size of the social group of that species. He extrapolated his findings to humans and concluded that on average each human is able to sustain roughly 150 stable social relationships. The number obviously varies by culture and historical epoch, but it’s a fairly reliable rule of thumb for contemporary humans. Note this is not “Facebook Friends”. These are people you know. People whose birthday parties you’ve attended. People you’ve shared the dance floor with at weddings. People with whom you have shared life’s joys and sorrows.

Now try to imagine those 150 people you actually know. And remember that our optimistic estimates are that COVID-19 will kill 1/149 people during the pandemic. This means that each person lucky enough right now to be living in an advanced country will lose someone they personally know to the disease. One of those people you know will die. One of those people at that wedding will die. Now recall how many people you have known who died to Influenza. Is COVID-19 just a flu? Decide for yourself.