The writer, an epidemiologist at the London School of Hygiene and Tropical Medicine, is the author of ‘The Rules of Contagion’
During all the major epidemics I worked on, there was speculation about the virus’s mutations. In general, these mutations are harmless, just random errors in the genetic code of a virus that do not change the way it infects or spreads. But every now and then, a collection of mutations emerges and dramatically changes the threat we face. In the past few weeks, researchers have noticed three worrying new variants of Sars-Cov-2 spread among the various strains of virus that circulate globally. These variants may well change the shape of the pandemic in 2021.
The first new variant was detected in southeastern England in the fall of 2020. It was of concern after it spread easily, despite control measures in place during November, overtaking existing variants to become dominant in much of the United Kingdom by end of December. Initial analyzes of contact tracking data and local epidemic growth suggested that this variant could be 40 to 70 percent more transmissible than previous viruses. Since then, it has been detected in other countries, with initial patterns in Denmark and Ireland consistent with its accelerated growth in the United Kingdom.
One of the challenges of a new variant is how to call it. Public Health England simply called it “Variant of Concern 202012/01”. The Covid-19 Genomics UK Consortium, which detected the variant, referred to it as “B.1.1.7” because it mutated the existing European “B.1.1” strain of the Sars-Cov-2 virus. The virus tracking platform Nextstrain dubbed it 501Y.V1, in honor of one of the mutations it had contracted.
Not long after 501Y.V1 was investigated in the UK, another variant – now known as 501Y.V2 – became a concern in South Africa. As the name suggests, he shared some mutations with his UK-based relative. , particularly a change in the “pico” protein that can help the virus attach to cells more easily. There were also some differences. While 501Y.V1 appears to transmit more readily in the UK, initial data suggests that immunity from past infection or vaccination should protect against it. In contrast, 501Y.V2 has a mutation that makes it better for preventing immune responses in laboratory studies. It does this by changing the appearance of the virus, essentially giving a familiar attacker a new cover.
As 501Y.V2 became dominant in South Africa, cases and deaths increased. This is despite evidence of considerable levels of antibodies after the epidemic wave of 2020 and the country’s next summer months.
There was a similar resurgence of enigmatic cases in Manaus, Brazil. Recent analyzes of antibody levels among blood donors suggested that the majority of the population was infected in 2020. However, in early 2021, hospitalizations and deaths increased again. This coincided with the detection of a third relative variant, 501Y.V3, which shares similarities with that of South Africa. In mid-December, almost half of the Sars-Cov-2 viruses analyzed in Manaus were 501Y.V3.
New outbreaks have also occurred in areas of Colombia and Peru that have substantial levels of antibodies from previous waves, leading to suspicions that new variants are also circulating there. Even though they do not cause more serious illness for individuals, increased transmission can mean many more cases – and therefore hospitalizations and deaths.
The emergence of three new variants with shared characteristics increases the possibility of “convergent evolution”, with viruses adapting independently to human populations worldwide. The many mutations in some of these variants – 23 to 501Y.V1 in the UK – suggest that they may have arisen in an immunocompromised patient; Chronic infections can give viruses a better chance of adapting than in a patient who recovers quickly.
So, where can all this lead? For viruses like HIV, there is evidence that evolution may eventually result in less severe variants, as a virus that kills hosts quickly may not spread as easily as one that causes a milder infection. Given that Sars-Cov-2 transmission tends to happen at the beginning of an infection, before someone becomes seriously ill, it is not clear whether a less deadly Sars-Cov-2 virus would have an evolutionary advantage over existing variants. However, as epidemics and vaccination campaigns lead to increased immunity, there may be additional pressures on the evolution of viruses. A recent study suggests that seasonal coronaviruses evolve gradually to escape the immunity generated in previous years, leading to reinfections over time.
During each epidemic, there is debate about how to deal with the next threat of disease. But these new variants – and the realization that there may be more out there undetected – suggests that this debate is no longer hypothetical. New strains must be treated as new threats and countries urgently need to decide how to tackle them.