The U.S. is now back to 10 new COVID-19 cases per 100K population per day, up 15% in the past seven days. That’s still far from uniform. New cases continue to decline in some parts of the country. By contrast, we’re starting to see sporadic re-imposition of mask mandates in locations with significant upticks in cases.
Data source for this and other graphs of new case counts: Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 4/12/2022, from https://github.com/nytimes/covid-19-data.” The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html
Reimposing mask mandates
Philadelphia is reimposing a mask mandate for indoor public spaces, in response to the rise in cases there. Based on the reporting, this is not an ad-hoc decision. Instead, when conditions meet pre-defined criteria, they re-impose a mask mandate. An automatic process of that type seems like a reasonable model going forward, but, weirdly, if I did the math right, the reported 142 new cases per day there is a rate of just 9 cases per 100K per day. So they have a plan, but the threshold seems quite low. Perhaps their criteria include more than just the new-case rate. But as plausibly, that low current new-case rate explains why (by report) Philadelphia is the first U.S. city to re-impose a mask mandate.
Separately, at least four universities in the Washington DC area have reinstated their mask mandates, again in response to an uptick in new cases.
As an economist, I think it’s particularly telling when private-sector organizations with group living quarters make a decision like that. If you infect a stranger, you don’t bear the cost of that. It’s “an externality”, a cost that you cause, but don’t have to pay for. Ditto if a stranger infects you.
But those cost-of-disease spread are internalized within a university. That is, if infection spreads widely enough within that defined student population, the university ends up bearing the cost in the form of disrupted in-person education. Unsurprisingly, throughout the pandemic, universities have tended to be more aggressive in imposing and keeping COVID-19 hygiene rules, up to and including mandatory testing and vaccination.
What I’m saying is that I’m not surprised that, once again, universities are on the leading edge of re-imposing COVID hygiene. In the general public, when you infect a stranger, well, that’s somebody else’s problem. By contrast, when one student infects another, that’s the university’s problem. A single economic entity bears the cost of failure to contain spread. The cost-benefit calculation for a university really is different from the same calculation for the general public.
Why the rise?
First, a rebound in new cases shouldn’t come as a surprise. As I’ve noted in prior posts, Great Britain and Australia never really got past their first wave of Omicron. Certainly not the way the U.S. and Canada did. They are only now passing the crest of their second Omicron waves, and they still have new-case rates that are far higher than those currently observed in the U.S.
Source: Johns Hopkins data accessed via Google search
Otherwise, I don’t think you can point the finger at any one cause.
For what it’s worth, it’s hard to blame this latest uptick entirely on the more-infectious son-of-Omicron (BA.2). As of the week ending 4/9/2022, the CDC estimates/projects that BA.2 accounted for about 86% of new cases. That’s up from the high-70-percents the prior week. My take on it is that any large impact of BA.2 would have been evident weeks ago. So it has a small impact on rate of disease spread, at most.
Source: CDC COVID data tracker.
Plausibly, changing behavior is a factor. The word has gotten out that if you’re vaccinated, in all likelihood, if you are infected, the case is apt to be mild. That, and low case rates, means that U.S.COVID-19 hygiene practices are reaching new lows for the pandemic.
Source: Carnegie-Mellon University COVIDcast.
And, I suppose, as with the recent Gridiron Club dinner in Washington DC, people are more willing to attend events that bear some significant risk of disease spread. For example, one of the attendees at that Gridiron super-spreader event was none other than Dr. Fauci. If he decided to green-light that event, who am I to say otherwise?
And then there’s the slow downward drift in immunity over time. Because the elderly were first to be vaccinated/boostered, and because immunity appears to fade faster in the elderly, this ought to result in a shift in the age mix of new cases. Unfortunately, there is no timely U.S. data showing the breakout of new cases by age.
FWIW, the last two weeks of data from Virginia show no such thing. The share of new cases arising from the elderly has fallen slightly. The share from young adults (age 18-34) has risen slightly. But no smoking gun in either case.
I’m not even going to hazard a guess as to what’s the principal cause of our turnaround in new cases. Likely, a handful of modest changes — in BA.2 share, in COVID-19 hygiene practices, and in underlying immunity — is enough to set cases rising again.
For myself, I think I’ve worked out what’s risky and not, for indoor spaces, in the current context. It really gets back to the poster that the Japanese Ministry of Health created at the start of the pandemic:
There’s a reason that, in almost every state, the first businesses to be shut down, and the last to be allowed to open, were the bars. Just think about a crowded place, where people are simultaneously drinking and shouting — and go somewhere else.
For example, my wife and I have gone back to seeing movies. Sitting 30′ from a few other people, and breathing, in a cavernous space — that’s about as far from a crowded, noisy bar as you can get. And so that’s well withing my current tolerance for risk.
