To get an early sense of what the heavily mutated Omicron variant has in store for the United States, look no further than Cornell University in Ithaca, N.Y.
On Tuesday, Dec. 7, Cornell conducted 5,456 tests and reported 27 COVID-19 cases on campus. That translates into a positivity rate of 0.49 percent. So far, so good.
But just six days later, on Monday, Dec. 13, the school reported 10 times as many cases (276) — despite conducting roughly the same number of tests (5,832).
In other words, Cornell’s positivity rate soared from less than half of 1 percent to almost 5 percent in the span of a single week.
When charted on a graph, a curve that steep doesn’t look like a curve at all. It looks like a vertical line.
Cornell has never experienced anything like it. More than 97 percent of the on-campus population is fully vaccinated; as a result, the school detected just 456 COVID cases during the spring 2021 semester and just 465 additional cases during the first three months of fall.
Yet now Cornell has logged 986 new cases over the last four days alone — and Omicron is probably to blame.
The latest on the Omicron variant
“Just last evening our COVID-19 testing lab team identified evidence of the highly contagious Omicron variant in a significant number of Monday’s positive student samples,” Cornell president Martha Pollack wrote Tuesday morning in an email announcing that the school would be shutting down campus and moving finals online, effective immediately. “The Omicron variant ... appears to be significantly more transmissible than Delta and other variants.”
Across the U.S., evidence is accumulating that Omicron is already spreading faster than any previous variant — particularly in the few places, like schools and sports leagues, that conduct mass testing. The NFL, for instance, had more than 70 players test positive on Monday and Tuesday alone, and the league is on track to detect more cases this week than ever before.
On Monday, the NBA postponed two Chicago Bulls games following a COVID outbreak that affected 10 of the team’s players. The Brooklyn Nets, the Milwaukee Bucks and the Los Angeles Lakers also had players test positive, despite a league-wide vaccination rate of 97 percent and an estimated booster rate of 60 percent — roughly triple the rate among U.S. adults as a whole.
The NHL also delayed three games due to a COVID outbreak.
Meanwhile, viral loads in Boston’s wastewater system are nearly double last year’s peak level. “The increase in the concentration in the wastewater is strongly suggestive of Omicron spread,” Mariana Matus, co-founder and CEO of Biobot Analytics, explained last week. Omicron has already been detected in sewage samples from Texas, California and Colorado.
Finally, the Centers for Disease Control and Prevention released new projections Tuesday showing that Omicron now accounts for 2.9 percent of U.S. cases, up more than sevenfold from 0.4 percent the previous week. In the New York and New Jersey area, the new variant already accounts for an estimated 13 percent of infections, according to the CDC. Over the last two weeks, cases in New York City have skyrocketed 120 percent.
Along with the Cornell outbreak, each of these data points suggests that the U.S. is about to experience what other countries are already starting to grapple with: exponential Omicron spread of the sort that will put America — which is currently enduring yet another big Delta wave — on track to reach previously unthinkable levels of COVID infection and transmission, shattering the country’s previous record (from Jan. 8, 2021) of 300,000 new cases in a single day.
In fact, that’s what just happened in the United Kingdom, where Omicron cases are doubling every 48 hours — an unprecedented growth rate — and where the new variant is already dominant in London. As in the U.S., U.K. case numbers previously peaked on Jan. 8 (at 68,053); on Wednesday, the U.K. easily broke that record with 78,610 new cases. London’s Omicron curve has also gone vertical, just like Cornell’s.
It’s a similar story in Denmark, where Omicron is equally pervasive. There, widespread testing is finding more than 117 new daily COVID cases per 100,000 residents — the highest rate of detection in the world (and more than three times the current level in South Africa, where Omicron was first discovered). Already, Denmark’s average daily case count is nearly twice as high as it was last December, during the Scandinavian country’s previous peak.
On Wednesday, European officials predicted that Omicron would become the continent’s dominant variant by mid-January.
This much, then, seems increasingly clear: Omicron is capitalizing on its many mutations to spread more readily and rapidly than even the hypercontagious Delta variant, in part because it is much better at dodging existing antibodies acquired through vaccination or previous infection.
The upshot, as virologist Muge Cevik of St. Andrews University tweeted Tuesday, is that “the only thing” we can be “sure of” is that Omicron "will spread so quickly through the population, making it likely impossible to contain even with the most stringent measures & giving us very little time over the next few weeks.”
So the question now isn’t whether Omicron will explode in the U.S. That’s a foregone conclusion. The question is how much severe disease Omicron will leave in its wake.
Many observers are eager to conclude that South Africa’s lower rate of hospitalization relative to cases means Omicron itself is intrinsically milder — that is, less likely to cause severe disease in anyone it infects. That’s one possibility. There’s even a mechanism that would explain such mildness. According to a new lab study, Omicron infects and multiplies about 70 times faster than the Delta variant in the human bronchus — the two large tubes that carry air from the windpipe to the lungs — but 10 times less efficiently in the lung tissue itself.
“Less efficient replication in the lungs may suggest lower severity,” Cevik explained — even as she cautioned that more clinical studies are needed to confirm this finding; that individual immune response also plays a big part in severity; and that Omicron’s higher viral load could still make it harder for some people to fight off.
The other possibility is that Omicron is no more or less severe than Delta. Rather, it’s simply infecting and/or reinfecting a lot of people other variants can’t reach but who still boast enough backup immunity — through vaccination or prior infection — to prevent severe disease this time around. Add a lot of otherwise avoidable “mild” cases to the mix, and a variant is going to look less severe — even if it’s just as likely as its predecessors to make unvaccinated or otherwise vulnerable people really sick.
The problem is that Omicron is likely to infect many, if not most, of these vulnerable people in fairly short order. Preliminary studies show that neither two vaccine shots nor natural immunity offers much protection against Omicron infection or transmission, which helps explain why the new variant is multiplying so quickly in countries such as the U.K. (70 percent) and Denmark (77 percent) that boast much higher full-vaccination rates than the U.S. (61 percent).
Booster shots can restore protection against infection to 75 or 80 percent, but just 17 percent of Americans have received one. Only about half of Americans over 65 — the most at-risk group for hospitalization — have gotten their boosters. Thirteen percent are still not fully vaccinated. That’s 7 million seniors. And more than 40 million U.S. adults haven’t gotten a single COVID jab yet.
So while young, highly vaccinated Cornell students are likely to shrug off Omicron, what happens when they return home and interact with some of these millions of still-vulnerable Americans over holiday break? More to the point, what happens if and when U.S. cases start to dwarf previous waves? What fraction of those cases become hospitalizations? What fraction become deaths? Even a small share of a very big number is still a big number — and the U.S. is about to find out just how big its COVID case numbers can get.