Omicron updates: Spreading rapidly in the U.S.

We keep learning about this dangerous variant as it spreads through the U.S. and the world. A few major updates from this week:

  • Omicron is spreading rapidly in the U.S. Last Tuesday, the CDC announced that Omicron had gone from causing 0.4% of new COVID-19 cases nationwide in the week ending December 4, to 2.9% of cases in the week ending December 11. That’s a seven-fold increase over the course of a week; the variant appears to be doubling every two to three days, based on data from the U.K. We can assume that it will be the dominant variant in the U.S. by the end of December, if not sooner.
  • U.K. data provides information on just how fast Omicron can spread. The U.K.’s comprehensive genomic surveillance system, combined with its unified national public health system, allows British researchers to analyze their country’s Omicron cases in high detail. According to the latest briefing from the U.K. Health Security Agency (summarized by Meaghan Kall): risk of reinfection with Omicron is three to four times higher than with Delta; risk of household transmission with Omicron is two to three times higher than with Delta; and the variant is doubling every two days—or even every 1.5 days, in some parts of the U.K.
Omicron’s rapid spread in London, compared with prior Delta cases. Chart by Theo Sanderson; see his Twitter for the full animated version.

  • New research from Hong Kong provides insight into why Omicron spreads so fast. Preliminary data from a Hong Kong University research team suggests that, within 24 hours of an Omicron infection, the virus “multiplied about 70 times faster inside respiratory-tract tissue than the Delta variant,” reports Megan Molteni at STAT News. More virus in the respiratory tract means more virus getting out into the air, Molteni explains. At the same time, the variant seems to be worse at multiplying within lung tissue, which may contribute to milder disease. While the Hong Kong study has yet to be peer reviewed, this finding aligns with reports of superspreading events among fully vaccinated people.
  • Skepticism about “Omicron being mild” continues despite more reports. Early this week, the largest health insurance company in South Africa posted results of a study examining the country’s Omicron wave. The study found that risk of hospitalization was 29% lower for Omicron patients than it had been during the country’s spring 2020 COVID-19 surge. While this finding follows other reports out of South Africa, experts are still skeptical: in part because it can take weeks for a coronavirus infection to progress to hospitalization, and in part because South Africa’s population has a lot of prior immunity from past surges and vaccinations. Also, a “milder” variant that’s more transmissible can still lead to significantly more hospitalizations.
  • We’re getting more evidence that vaccination protects against severe disease from Omicron. Basically: two shots are good, three shots are better. “Though these data are preliminary, they suggest that getting a booster will help protect people already vaccinated from breakthrough or possible severe infections with Omicron during the winter months,” writes NIH Director Dr. Francis Collins in a recent blog post summarizing both laboratory and real-world studies. If you’re eligible for a booster and haven’t yet gotten it, now is a great time.
  • But: We don’t know how well vaccines protect against Long COVID from an Omicron infection. As many experts continue to say that Omicron cases are mild for those who are vaccinated, the Long COVID experts and advocates I follow have pointed out that a mild breakthrough case can still lead to this prolonged condition. “Omicron is a huge individual threat,” wrote Long COVID researcher Hannah Davis on Twitter recently. “A 15-30% chance of being disabled for at least a year, but likely for the rest of your life, is a bigger threat than most of us ever faced ever before the pandemic.”
  • New York City is an Omicron hotspot in the U.S. As I noted in today’s National Numbers post, this variant has clearly hit NYC, as seen in record case numbers and felt in long lines for testing throughout the city. According to CDC estimates, Omicron was causing about 13% of new cases reported in New York and New Jersey in the week ending December 11. One week later, knowing how fast Omicron has outcompeted Delta in the U.K. and elsewhere, we can assume that it’s now causing the majority of cases in this region.
  • Other U.S. states and regions may be behind in their Omicron sequencing, so assume it’s spreading in your area even if it hasn’t been officially identified yet. As I’ve written before, genomic surveillance in the U.S. is geographically very spotty. NYC is a clear hotspot, but it’s also a city with a lot of sequencing infrastructure. In other parts of the country, Omicron may not have been formally identified yet—but that doesn’t mean it isn’t spreading. Take Orlando, Florida as an example: wastewater sampling in the surrounding county found that Omicron was completely dominating the community this week, according to AP, even though “practically no cases of clinical infection” have been reported.
  • Good news: South Africa’s case numbers are now trending down. As of yesterday, COVID-19 case numbers in Gauteng, the center of South Africa’s COVID-19 outbreak, as well as in other parts of the country, seem to be turning around. Computational biologist Trevor Bedford offered some potential explanations in an interview with New York Magazine: limited testing capacity and milder disease may lead to underreporting of COVID-19 cases in South Africa; less of the population may be susceptible due to prior immunity; and the variant may spread so fast that it can quickly burn through social networks and other avenues of transmission. We’ll need to see whether South Africa’s decline holds, and whether we see similar patterns in other Omicron hotspots.
  • The U.S. is not prepared for an Omicron surge. If you haven’t yet, take some time today to read Ed Yong’s latest feature in The Atlantic, which discusses how the U.S. has failed to learn from past COVID-19 outbreaks and prepare for the Omicron surge that has already arrived. “Rather than trying to beat the coronavirus one booster at a time, the country needs to do what it has always needed to do—build systems and enact policies that protect the health of entire communities, especially the most vulnerable ones,” Yong writes.
  • Omicron has altered the trajectory of the pandemic. Another piece to take time for today is this article in Science by Kai Kupferschmidt, discussing the “really, really tough winter” that scientists now see coming. Kupferschmidt explains that, even if many Omicron cases are mild, the variant is still spreading fast enough that it could land a lot of people in the hospital. In addition, the variant “may bring other, unpleasant evolutionary surprises” if future coronavirus variants evolve out of Omicron, Kupferschmidt writes.

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