Thanks for the response. I hadn’t seen that post before my last reply.
I still wonder about the statement that the new variants are spreading fast. Where are the numbers on that being published?
Testing in the lab demonstrates that the new variants are more efficient at spreading and spot checks show them popping up more and more frequently, suggesting they’re edging out the old variant. Taken together, those two bits of information fit in with the existing understanding for how mutations for infectious diseases work: if it enables you to infect more hosts, the mutation becomes dominant. If it makes you less effective at spreading, it tends to die out due to competition.