The Covid-19 virus is evolving rapidly.
That should come as no surprise: RNA-based viruses generate mutations constantly as a result of their error-prone replication. Wherever there are more infections, there are more opportunities for the virus to mutate. For a virus new to a species, as this coronavirus is to humans, some mutations are likely to make it more transmissible.
Important new coronavirus variants have emerged in the United Kingdom, Brazil, and South Africa. What is worrisome about these variants is that even though they evolved independently, they have some similarities. All share the N501Y mutation in the virus’s immunologically key spike protein. The strains in South African and Brazil also share the E484K mutation in the same protein, which some experiments suggest may at least partially evade the antibody response people generate after infection with older strains.
A newly emerging lineage called P.1 with multiple spike protein mutations was identified in 42% of samples tested in December from Manaus, Brazil. The largest city in the Amazon region is being severely hit by the Covid-19 pandemic for a second time: It experienced a similarly fierce first wave in April 2020, leading some to conclude that the population achieved close to herd immunity. That conclusion was wrong, and two possible explanations are that immunity either waned or does not fully protect against P.1.
Multiple scientific groups, including ours, have estimated that the so-called variant of concern in the U.K. (B.1.1.7) is more transmissible than previous coronavirus variants, with estimates varying between 40% and 80%. This likely explains the rapid growth in case numbers seen in Southern England and Ireland over the last two months of 2020. Recently, several groups have reported increased disease severity in people infected with the B.1.1.7 strain compared to those infected with previous strains.
How can policymakers respond to these new challenges? Being aware of them would be a good start. Only a handful of countries, such as the U.K. and Denmark, have large-scale systematic surveillance in place to sequence the genomes of a large enough sample of viruses to track the evolution and rise of new variants in real time. When potentially significant new variants are detected, any changes in transmission, severity, or immunity need to be characterized as quickly as possible.
As countries roll out mass immunization, changes affecting immune recognition will be particularly important to watch for to update vaccine formulation if needed. Fortunately, this pandemic has seen the pioneering of the new technology of mRNA vaccines, such as those produced by Moderna and Pfizer, which should be able to be updated much more easily than older vaccine technologies.
Maintaining control of more-transmissible coronavirus variants is the second challenge. As far as we can judge, B.1.1.7 is no different in how it spreads, it is just better at it in all settings. The same interventions that have been used throughout this pandemic — social distancing, mask wearing, and hand washing — work against the new strains, but their increased transmissibility means that these measures must be implemented more stringently to control the pandemic. ...
