This weblog started in the spring of 2002, in the wake of 9/11. Like much of the early blogosphere it was inspired and precipitated by armchair punditry that bubbled up out of the interwebs in the wake of that exogenous shock. Similarly, a whole set of financial blogs (e.g., Calculated Risk) popped up in the wake of the 2008 financial crisis. Crises seem to lead to changes in the information ecosystem.
In 2020 blogs are passe and most of the action of the “discourse” happens on Twitter and YouTube channels. But I’m still here, passing through multiple exogenous shocks, observing the world. To be frank, I think the coronavirus shock has the potential to be bigger than both 9/11 and the financial crisis combined. I have three children. One will remember quite clearly the pre-coronavirus world. One will be quite vague about it but have some fragments of memories before. And one will never know a world that wasn’t shocked by the coronavirus.
You wonder, could it be that big? In the middle of February, I began to consider how “big” the impact could be. Without major interventions, I assumed that the virus could infect ~30% of the American population, with a conservative case fatality rate of ~0.5%. In the United States of America, this yields about 500,000 fatalities. As it happens, this is less than the 600,000 who die of cancer every year. So what’s the big deal then?
First, these are to some extent excess deaths (presumably some of the individuals who will die of COVID-19, the disease, would have died of cancer or heart attacks the same year). Second, cancer is not contagious to doctors and nurses. In general, cancer is not contagious at all (some of the causes of cancer, like infection, can be contagious). Third, the treatment of cancer is generally a well-understood set of procedures (of various levels of effectiveness). Coronavirus, far less so. The stress on the medical system will be much greater and produce opportunity costs. This brings us to the biggest issue: the illnesses may come in a wave, and so overwhelm the medical system. Cancer occurs throughout the year.
I passed my numbers by a few people (e.g., Spencer Wells), and they thought they weren’t crazy, though they quibbled on particular parameter values here and there. By the middle of February I was becoming quite concerned, and, some of the people who along with me were quite sanguine around February 1st were now quite concerned as well. On February 28th I expressed my panic in a candid manner on Twitter. There were others who were like me. From a geneticist friend on March 2nd:
I have been trying to raise awareness in our local community through Nextdoor, and it has been very painful.
Especially because this is a very conservative area and somehow this has gotten politicized so that pro-Trump people think the coronavirus is just a cold
March 8th was the last time I was “out”, and I had a conversation with a neighbor who has a Ph.D. When my eyes started getting wild, and I told her she wasn’t going to see us for a while, she clearly thought I was crazy judging by her expression. On March 11th, she texted us that she was keeping her daughter home from school too.
But some people are still sanguine. To be frank, most of the skeptics of the impact of coronavirus are not very smart. I don’t say that judgementally, but a lot of the smart people who are skeptics seem to be keeping their mouths shut because of the taboo. The New York Times has a piece, Some Ask a Taboo Question: Is America Overreacting to Coronavirus? It’s ridiculous that such a piece even has to be written! Meanwhile, my friend Heather Mac Donald presented the skeptical take in her usual trenchant style over at New Criterion, Compared to what?
Some people reacted to Heather’s piece emotionally. Their reaction was basically “I can’t even!” I don’t think that’s what you should do. Lives and societies hang in the balance, and we need to remain rational. Entertain even views we consider offensive. This is a matter of life and death, not psychic trauma or metaphorical violence.
There are two skeptical takes from a more purely analytical perspective that I want to bring to your attention, A fiasco in the making? As the coronavirus pandemic takes hold, we are making decisions without reliable data, by John Ioannidis, and Coronavirus Perspective. I did not find Ioannidis’ piece persuasive because it relied too much on extrapolating from the Diamond Princess cruise. We now have Iran, Italy, and much of Western Europe. We also have the rest of Asia. I found the Epstein piece far more interesting because I made many of the same points in the last week of January and the first week of February to my wife.
Let me quote Epstein:
First, they underestimate the rate of adaptive responses, which should slow down the replication rate. Second, the models seem to assume that the vulnerability of infection for the older population—from 70 upward—gives some clue as to the rate of spread over the general population, when it does not. Third, the models rest on a tacit but questionable assumption that the strength of the virus will remain constant throughout this period, when in fact its potency should be expected to decline over time, in part because of temperature increases.
In relation to the first issue, I argued in early February that perhaps China, and Hubei, is different. We don’t know the comorbidities that are unique, and we don’t know if the Chinese healthcare system is particularly vulnerable. With foreknowledge, other nations will adapt and adjust. The spread of the pandemic to Iran and Italy, and now Spain and perhaps France and parts of the USA, indicates that the replication rate, R0, isn’t that different across societies without extreme measures. That is, the R0 ~ 2.5 or so.
In China, they drove it down to ~ 0.3 with an incredible vice grip of control. I see no evidence right now that we in the West will replicate that, though some nations are finally moving (France).
Second, from what I have seen many of the same broad patterns reported by the WHO in China have replicated in many other societies. And, the infection rate for children according to WHO is the same, with lots of passive spreaders. It is probably true, as Epstein argues, that the virus is targeting the most vulnerable first. But until we see real drop in case fatality rate I’m not sure that it’s swimming in the shallow end of the pool.
Last, the issue of evolution toward lower virulence, I’ve made this point. We shouldn’t assume that R0 and c.f.r. are fixed values. They may change. When I asked Greg Cochran his intuition on reduced virulence, he thought it would take years. That’s just too long for the present pandemic.
R0 and c.f.r. will change, probably for the better. But my wife watched the Wuhan epidemic closely, and we saw its rise, and how it fell, and what transpired in the interim. It was not pretty. There were cases of infected parents snatched from homes, leaving behind a small child who was fed through a hole in the door by neighbors. The child had no idea what was going on.
This sort of rapid and unconstrained isolation of infected individuals is unlikely to happen in the West. At least for now.
Reading the Epstein piece it’s hard for me to deny that I would have asserted its plausibility on February 1st. He says: “It is highly unlikely that there will ever be a repetition of the explosive situation in Wuhan, where air quality is poorer and smoking rates are higher.” Again, I said similar things. But the Italy case, in particular, illustrates that COVID-19 can impact very different societies. I think we need to update this prior.
As of this writing, COVID-19 has had a mild impact on tropic Asia and Africa. This is peculiar because Chinese influence and contact across this region are ubiquitous. One of the reasons given for why Iran and Italy have been hit so hard is that they are economically intertwined with China. But much of Africa and Asia is similar. As of a few years ago, there were a million individuals of Han ethnicity living in Africa.
The primary explanation here is heat and humidity mitigating and retarding spread. Since I lasted talked about this more preprints have come out. Spread of SARS-CoV-2 Coronavirus likely to be constrained by climate and High Temperature and High Humidity Reduce the Transmission of COVID-19.
There are many hypotheses for why many viral infections are seasonal. UV light, people dispersing from indoors, absolute humidity, and temperature, are all candidates. No one knows for sure. When COVID-19 began to spread initially some researchers said there was no reason to think it would be seasonal. Though I think this is too strong (other coronaviruses are often seasonal), it was defensible. But the tardiness of the pandemic in urban Lagos, Bangkok, and Mumbai, as opposed to Seattle, Milan, and New York City, is suspicious. I think the most likely reality is that the “environment” (hot and humid) does have a mitigating impact on the spread. This means there is hope in the temperate latitudes as it gets warmer and more humid. I am not certain about this, but this is my own best guess.
One of the primary ways in which high absolute humidity prevents the spread of influenza is by increasing the size of expelled droplets, which fall to the ground. There is now a debate about whether SARS-CoV-2 spreads in aerosolized form or through surface contact. The WHO is still saying there is no airborne spread, while American researchers disagree. I think the Americans are right, as it explains the R0 better, and the different regional patterns.
Today I wrote about blood group differences in susceptibility. A reader pointed out that there is a mechanistic explanation in the case of SARS-CoV-1. I think that this phenomenon is probably real, in which case areas with very high fractions of O, such as Africa and Latin America, have a bit more slack. If individuals with blood group O are 30% less likely to get infected, that’s going to impact the R0 as a function of the proportion of the population that is O (in Chile it is 85% in Congo it is 60%). This does not mean you are “immune,” but, it does mean on a population-wide scale it makes a difference.
I have not talked extensively about ethnic differences in disease susceptibility. This is a thing. And sometimes it is harder to adduce than simple blood group differences (on average). But the empirical evidence of Iran and Italy suggest to me that genetic variation between groups in a coarse sense is not a major issue (one of the first British to die was of Bengali ethnic origin). When the COVID-19 GWAS is finished we’ll know a lot about individual and group susceptibility. But right now, we know that pretty much every group is at risk.
What’s the bottom-line here? Modeling is great, but we need more empirical data, though we do have some empirical data. The examples of Iran and Italy suggest that unfortunately, the Wuhan dynamics are pretty exportable and not sui generis, as we’d hoped. Hopefully, we’ll see some nations spared due to their unique conditions, which would lead us to believe that the whole world doesn’t need to engage in extreme containment strategies such as in Wuhan.
I’ve given less thought to social and economic consequences, but I’ll have a follow-up post where I tackle that issue.
Addendum: Not to forget, both age and density probably matter. Younger populations get infected, but are often asymptomatic. It is almost certain that lower density environments will exhibit less spread. Antique Old World cities are probably better for spreading this disease than American suburbs and exurbs.