What is going on? How can increased levels of Omicron virus replication be associated with reduced disease? How did so many mutations in the receptor binding domain of Omicron arise, apparently spontaneously? Why do the evolutionary tree plots show that Omicron represents a separate branch from currently circulating viruses? How could so many mutations which confer vaccine resistance suddenly appear?
Botswana (and Southern Africa in general) does not have a very high vaccination rate, so why would a vaccine-resistant virus strain develop in this region. Did someone engineer and release yet another virus? Lots and lots of questions. Very few answers. And then this new press release from the University of Hong Kong arrived today, showing that Omicron replicates more highly in conducting airway cells (bronchus), and less in lung cells. I think that the paper above provides with some important clues that could help us make sense out of this puzzle…
This is why this new finding from a team at Hong Kong University is so significant. Because it indicates that what may be most important about Omicron may not be the ability to evade vaccine-induced immunity, but that it has shifted its preferred tissue target for infection and replication to the upper airway instead of deep lung. That could explain why it is more infectious, replicates to higher levels, and yet causes less severe disease.
Let’s hope that is our best gift this Christmas.