The writer, an epidemiologist at the London School of Hygiene and Tropical Medicine, is the author of The Rules of Contamination.
During every major epidemic I’ve worked on, viral mutations have been speculated. Mostly these mutations are harmless, just random errors in the genetic code of the virus that do not change the way it infects or spreads. But from time to time, collections of mutations appear and drastically change the threat we face. In recent weeks, researchers have spotted three disturbing new variants of Sars-Cov-2 scattered among the various viral lines circulating around the world. Such options could change the shape of the pandemic in 2021
The first new option was discovered in the South East of England in the autumn of 2020. It caused concern after it spread easily, despite control measures introduced in November, outpacing existing options to become dominant in much of the UK by the end of December. . Early analysis of contact tracking data and local epidemic growth suggests that this option may be 40 to 70 percent more susceptible than earlier viruses. It has since been discovered in other countries, with initial models in Denmark and Ireland corresponding to its accelerated growth in the United Kingdom.
One of the challenges with the new version is how to call it. English public health simply called it “Option of Concern 202012/01”. The consortium Covid-19 Genomics UK, which discovered the variant, called it “B.1.1.7” because it mutated from the existing European line of viruses Sars-Cov-2 “B.1.1”. The Nextstrain virus tracking platform named it 501Y.V1 after one of the mutations it had collected.
Not long after 501Y.V1 came under control in the UK, another option – now known as 501Y.V2 – became a problem in South Africa. As the name suggests, he shares some mutations with his UK-based relative, in particular a change in the “spike” protein, which can help the virus attach more easily to cells. There were some differences. While 501Y.V1 seems to be more easily transmitted in the UK, early evidence suggests that immunity from past infection or vaccination should protect against it. In contrast, 501Y.V2 has a mutation that makes it better at avoiding the immune response in laboratory tests. This is done by changing the appearance of the virus, essentially giving the known intruder a new cover.
As 501Y.V2 became dominant in South Africa, cases and deaths increased. This is despite the evidence of significant antibody levels after the epidemic wave in 2020 and the upcoming summer months in the country.
There was a similar puzzling resurgence of cases in Manaus, Brazil. A recent analysis of antibody levels among blood donors suggests that the majority of the population is infected in 2020. However, in early 2021, hospitalizations and deaths are rising again. This coincided with the discovery of a third in terms of variant, 501Y.V3, which shares similarities with that in South Africa. By mid-December, almost half of the Sars-Cov-2 viruses analyzed in Manaus were 501Y.V3.
There are also new outbreaks in areas of Colombia and Peru that have significant levels of antibodies from earlier waves, leading to suspicions that new variants are spreading there as well. Even if they do not cause more serious illness to individuals, increased transmission can mean many more cases – and hence hospitalizations and deaths.
The emergence of three new variants with common characteristics increases the possibility of “convergent evolution”, as viruses adapt independently to human populations around the world in similar ways. The many mutations in some of these variants – 23 for 501Y.V1 in the UK – suggest that they may have occurred in an immunocompromised patient; chronic infections may give viruses a better chance of adapting than in a patient who recovers quickly.
So where can all this lead? For viruses such as HIV, there is evidence that evolution may eventually lead to less severe variants, as a virus that kills hosts quickly may not spread as easily as one that causes a milder infection. Given that transmission of Sars-Cov-2 tends to occur at the onset of infection before someone becomes seriously ill, it is not clear that the less lethal Sars-Cov-2 virus would have an evolutionary advantage over existing options. However, as epidemics and vaccination campaigns lead to increased immunity, there may be additional pressure on viruses to develop. A recent study suggests that seasonal coronaviruses develop gradually to avoid the immunity generated in previous years, leading to re-infections over time.
During each epidemic, there is a debate about how to deal with the next threat of disease. But these new options – and the realization that there may be more undiscovered – suggest that this debate is no longer hypothetical. New strains must be treated as new threats and countries must urgently decide how to deal with them.