It doesn’t add up. Omicron’s distinguishing features are that it spreads fast and that the entire population is vulnerable to catching it. The only people with a decent degree of protection against infection are the boosted, and South Africa hasn’t rolled out boosters yet. Even if they had, plenty of boosted people here and abroad have tested positive. The latest example is Elizabeth Warren.

A virus that can infect everyone should be able to burn for a good long awhile even if it’s burning very hot.

So why have cases in South Africa dropped for five days in a row?

#COVID19 UPDATE: A total of 28,520 tests were conducted in the last 24hrs, with 8,515 new cases, which represents a 29.9% positivity rate. A further 105 #COVID19 related deaths have been reported, bringing total fatalities to 90,453 to date. See more here: https://t.co/5ChLKPzyWb pic.twitter.com/3ZUpl6cMO1

— NICD (@nicd_sa) December 20, 2021

Gauteng province, where the Omicron outbreak erupted, isn’t even the province with the highest number of cases at this point. Scott Gottlieb is happy but mystified:

In South Africa, we’re thankfully seeing a striking decoupling between new Covid cases and ICU admissions and deaths. Whether #Omicron is inherently less virulent, whether this hopeful finding is result of baseline immunity in infected, or a combination of both, is still unclear. pic.twitter.com/xtmCSdpCNc

— Scott Gottlieb, MD (@ScottGottliebMD) December 19, 2021

Trevor Bedford, a top virologist in Seattle, was recently asked by New York magazine what he thinks might be going on and spitballed several possibilities. It could be that South Africa is running short on tests, that the true number of cases is actually wildly greater than we realize. Or they may have enough tests but the mildness of Omicron in most patients is leading people to not bother getting tested. If they’re over it in a few days with nothing worse than a sore throat or whatever then they might not feel compelled to seek formal confirmation that they have it.

It could also be that not everyone is equally susceptible to infection by Omicron. For instance, although those with prior immunity can catch it, conceivably the variant is mostly preying on the non-immune. To the extent that it’s infecting the immune, many/most might be asymptomatic and not realize it.

And of course, as Omicron spreads and people recover from it, they gain immunity from the variant, closing off pathways of transmission. Some combination of all of those factors is contributing to the Omicron slowdown, Bedford believes. If he’s right, America’s wave could be similarly brief. After all, the share of our population that enjoys some form of immunity from COVID is likely at least as large as South Africa’s.

As Europe’s experience with the variant grows, evidence is emerging there too that the average person’s experience with Omicron will be less of an ordeal than with previous variants. For instance:

Actually, more recent data from Denmark looks more encouraging. Based on a far larger sample size, Omicron hospitalisations are at ~0.6% vs. ~1.5% for Delta (~60% down).
(Thanks @RufusSG for spotting the report)
8/https://t.co/ALkZLAXDvv pic.twitter.com/zKJfTohuT2

— Prof Francois Balloux (@BallouxFrancois) December 19, 2021

In the UK, one town that experienced an explosive surge of Omicron cases hasn’t seen hospitalizations surge in parallel. Data from a week ago found hospital admissions at just 11 percent of what they were at their peak last winter. Maybe Omicron is much ado about nothing.

Scientists in Britain and Denmark aren’t betting that way, though. Those two countries are esteemed for their capabilities in genomic surveillance; Denmark is also highly vaccinated, with upwards of 80 percent having received two shots. Even so, Danish experts are grim about what lies ahead. It’s the same refrain from them as from so many other infectious disease experts recently: If Omicron is destined to infect something like half the population because of its contagiousness and immune-puncturing ability, even a tiny percentage of a sample that gigantic experiencing severe illness would wreak havoc on a nation.

“The next month will be the hardest period of the pandemic,” said Tyra Grove Krause, the chief epidemiologist at Denmark’s State Serum Institute, a campus of brick buildings along a canal…

“This will overwhelm hospitals,” Grove Krause said. “I don’t have any doubt about it.”…

Denmark’s hospitals have never had more than 1,000 covid 19 patients at any given time, last winter’s peak. But by early January, in a moderate scenario, hospitals could be seeing 500 new covid patients arriving every day. If omicron’s transmissibility winds up on the higher end, and it proves just as severe as the delta variant, with a strong ability to evade vaccines, daily admissions could reach 800.

Read that last paragraph again. The peak of COVID hospitalizations in the U.S. to date was 138,000 last winter. Imagine if 70,000 people needed to be hospitalized for Omicron *on a single day.* And then an even greater number needed to be hospitalized the day after that, and then the day after that. What happens?

Some of the worst-case scenarios being kicked around by UK scientists are mind-boggling:

The government’s SPI-M-O group of scientists, which reports to the Scientific Advisory Group for Emergencies (Sage), also warned that, based on their modelling, hospitalisations could peak between 3,000 and 10,000 a day and deaths at between 600 and 6,000 a day…

The advisers suggested reintroducing measures “equivalent to those in place after step 2 or step 1 of the roadmap in England”. Rules at that time included the “rule of six” and just two households meeting; they also barred holidays abroad, while care-home residents were allowed only one regular visitor.

The U.S. has five times the population the UK does. Per capita, a worst-case scenario death rate akin to the one the British are foreseeing would mean 30,000 Americans dead. Each day. Even the low-end UK estimate of 600 dead per day would shake out to 3,000 here, among the worst tolls of the pandemic. So much for the “mild” variant.

And if it’s that bad here and in the UK, imagine what it’ll be like abroad. At the moment, all evidence suggests that Pfizer and Moderna are the only vaccines that stand a reasonable chance of limiting infections by Omicron. Any country where those vaccines aren’t used is at risk of unchecked spread.

If Omicron burns out here as quickly as it seems to be doing in South Africa, we’ll avoid catastrophe. But a lot is riding on luck now. I’ll leave you with this.

A message from our health systems in today’s Plain Dealer. pic.twitter.com/B60AnzgBJu

— Kaitlin Durbin (@njKaitlinDurbin) December 19, 2021