Omicron Update

December 15, 2021 By Alan Salzberg

Today felt a lot like March 10, 2020.  A cascade of reports about outbreaks, and then a bunch of closures. Universities (Cornell, Princeton, Penn, NYU) and a bunch of Broadway plays.  At Cornell, cases went from 37 a day a week ago (and much lower 3 weeks ago) to 370 yesterday.  At my daughter's HS, several cases were reported, after never having more than 1 in a day all semester.

More generally, the CDC reported that Omicron cases went from less than 1% of cases to 3% in a week.  In NY and NJ, they comprise 13% of cases.  Unfortunately, the CDC did not give the total number sequenced or whether the sequencing was at random, so it's hard to know how far off these estimates, which are based on a small fraction of total cases, might be.  However, it's clear that Omicron is widely spreading in the US and is extremely contagious.  Some details are not known, such as : is it actually more contagious than Delta or is it spreading much faster because it spreads easily among people who were vaccinated and people who had already been infected (or both)?  

In any case, it is clear that we are going to have an avalanche of cases soon.  Two questions we do not know the answer but which I will shed a little light on, are below.

1. How high will cases go?

Everyone is talking about exponential growth again, and Omicron appears to be increasing around 4x per week here.  But this wont last forever.  If we assume the 4x rate continues, we'd have and if we conservatively estimate 1,000 Omicron cases now, we'll have a million in 5 weeks and a billion (more than the US population) in 10 weeks.  So this assumption is absurd.  However, there is the very real question of when it will abate.  Looking at South Africa, there is reason to be hopeful.  They first passed 1,000 cases on Nov 22 (when they were at 1,526--you can download the data in from their NICD site at ).  One week later (Nov 29), cases had increased five-fold.  In another week (Dec 6) they had increase between two and three fold.  In the last week, Dec 7 through 14, their week/week change averaged only 60% (they are now at around 25,000 cases).  So the increase is still large but is not the enormous change we saw at first.  Positive rates have fallen also, indicating that the flattening isn't due to them running out of tests.

This is not to say South Africa=US exactly.  Rather, it's common to see dramatic changes early and the increases flattening relatively quickly.  This has happened in every outbreak of Covid in every locality for which I've seen data, whether or not there were restrictions.  Will we see the highest level of cases in the pandemic?  Well, we are at about half teh daily average peak of 250,000 right now, and the delta outbreak is causing a biweekly increase of nearly 50% already. Therefore, I think the answer to that is likely yes, because even using conservative assumptions, we still have four facts against us: 1) we have a large national delta outbreak now, 2) it's prime Covid season (cold weather) in almost all the US, 3) it's extremely unlikely most of the country will institute many restrictions, and 4) Omicron will surely contribute some.  

So the news there was already bad and Omicron just worsens it, in other words.  However, it could be that Omicron is a quick outbreak that flares out, or it could be it's the outbreak to end all outbreaks.  We just don't know yet.  We can hope it's more like what South Africa looks now, with increases slowing substantially after a few weeks of enormous growth.

2. Are we about to have serious stress or collapse of some of our healthcare system?

The bad news here is that it's already happening with the Delta outbreak in places like Minnesota, and surely other localities will see this.  The good news is that in places with high vaccination + prior infection rates, like NY City, hospitalizations are a fraction of their peak.  Right now, despite more than doubling in the last few weeks, NYC Covid hospitalizations are at 932, far below last winter's peak of about 4,000, which itself is a fraction of the April 2020 peak of around 15,000.  So, while we of course don't want more hospitalizations, here in NYC there is capacity to spare for a surge (but of course not infinite capacity).

To be clear, this good situation does not extend to upstate New York.  In Western NY for example (see all data here, btw), hospitalizations are already at the pandemic peak, of 39 per 100,000 (contrast this to NYC's current 10 per 100,000).  Overall, in the US, the current number is about 20 per 100,000, and the peak was more than double that.  In terms of over-stressing the healthcare system, though, it's very localized--it's very hard to move patients even a few miles, much less dozens of miles.  During the peak of the pandemic here in NY, many patients died at full hospitals because they could not be easily transferred to hospitals even a few miles away.

So, it seems that Omicron will almost surely over-stress hospitals in communities with lower vax/prior infection rates.  If Omicron peaks well above our current all-time high, places with high vaccination rates may not be spared either, depending on how severe Omicron is for the vax/prior infection population.  Keep in mind that a bad flu season stresses hospitals, too, and flu is on average less severe than Covid (in the unvaxed/no prior infection population).  This means that even if Omicron is far less severe on average, hospitals in high vaxed areas will also be stressed will be operating at capacity+ if there is an outbreak that is substantially larger than last winter.

We'll know much more in a week or two, but that's the not-so-good news of the day.