1) In its #COVID19 epidemiological report this week, the World Health Organization noted the stealth #Omicron sub-variant BA.2 was “steadily increasing” in its spread, particularly in South Africa and Denmark. In this thread, I will report the latest developments concerning BA.2. 
2) The WHO found that BA.2 prevalence soared from 27% in South Africa on Feb. 4 to 86% by Feb. 11. In Denmark, BA.2 prevalence climbed from 20% in the last week of 2021 to 66% by the third week of January. These two countries are now recording rises in #COVID deaths. See below.
3) “Early evidence from limited studies suggest BA.2 is more transmissible as compared with BA.1,” the WHO concludes in its report. “Estimates of growth rates in Denmark indicate that BA.2 is 30% more transmissible than BA.1.”
4) Meanwhile, the authors of a pre-print study by University of Japan researchers recommended on Monday that “BA.2 should be recognized as a unique variant of concern, and this SARS-CoV-2 variant should be monitored in depth.” Why did they make this recommendation?
5) The Japanese researchers found that BA.2’s “genomic sequence is heavily different from BA.1.” BA.2 also possesses a higher effective reproduction number, higher fusogenicity (fusing to cells) and higher pathogenicity (the ability to cause disease) than BA.1.
6) What’s more, the researchers observed “vaccine-induced humoral immunity fails to function against BA.2 like BA.1, and notably, the antigenicity of BA.2 is different from BA.1.” And previous research had shown original Omicron was “markedly resistant” to the current vaccines.
7) Worse yet, the BA.2 sub-variant may also cause more severe disease. Experimenting on hamsters, the University of Japan researchers discovered that the lab animals infected with BA.2 got sicker and had worse lung function.
8) A separate pre-print study by New York researchers published on Tuesday found that BA.2 “is not neutralized…by any of the therapeutic monoclonal antibodies, including Sotrovimab and Evusheld.”
9) This latest research suggests that BA.2 poses a much greater risk to public health than previous #coronavirus strains and why Scientific American has described Omicron (including BA.2) as the “fastest-spreading virus in human history." scientificamerican.com/article/omicro…
10) Both Denmark and South Africa were hit by the original Omicron strain earlier than other countries, and then they were both buffeted by BA.2, which either prolonged their #COVID death waves or perhaps caused two ones in a row. Please see the chart below.
11) Do the trends in Denmark and South Africa mean that Québec, the rest of Canada and the United States will most definitely be hit with a BA.2-driven mortality surge in the coming weeks? Not necessarily. Here’s why.👇
12) The WHO epidemiological report notes that BA.2 prevalence has also ramped up in the United Kingdom and the United States, but #COVID deaths have not seemed to rise accordingly. See the chart below that goes back to Jan. 19 of this year.
13) But the WHO report also found that the prevalence in the U.K. (12% on Jan. 12) and in the U.S. (3.6% in the week ending Feb. 5) thus far has been much lower than in Denmark and South Africa. This suggests that perhaps BA.2’s true impact has not yet been felt.
14) Regardless, the timing of BA.2 couldn’t be any worse. Jurisdictions around the world are lifting public health protections, and fighting may soon erupt along the Ukraine border, which would hasten BA.2's spread — the topic of my last thread. The End.
https://twitter.com/Aaron_Derfel/status/1494508454249123850
15) ADDENDUM: "But the pandemic's really over!" say the disbelieving. "In fact, the conditions are ideal for more transmissible, more dangerous variants to emerge," the WHO's director-general declared Friday, the day after 3,187 Americans died from #COVID.
https://twitter.com/i/status/1494717410460512262
16) ADDENDUM 2: In Québec, chief public health officer Luc Boileau estimated earlier this week that up to 15% of Montréal's new #COVID infections have been caused by BA.2. Denmark was roughly at that prevalence in mid-December, two months ago, and BA.2 continued to rise there.
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