New Covid variants are a danger to all of us

The writer, epidemiologist at the London School of Hygiene and Tropical Medicine, is the author of “ The Rules of Contagion ”

In every major outbreak I’ve worked on, there has been speculation about viral mutations. Most of these mutations are harmless, just random errors in a virus’s genetic code that don’t change the way it infects or spreads. But every once in a while a collection of mutations crop up that drastically changes the threat we face. In recent weeks, researchers have noticed three disturbing new variants of Sars-Cov-2 scattered among the different lineages of viruses circulating around the world. Such variations could well change the shape of the pandemic in 2021.

The first new variant was detected in the south-east of England in the fall of 2020. It raised concerns after spreading easily, despite control measures in place in November, overtaking existing variants to become dominant in much of the UK by the end of December. Early analysis of contact tracing data and local epidemic growth suggested this variant may be 40-70% more transmissible than earlier viruses. It has since been detected in other countries, with initial patterns in Denmark and Ireland consistent with its accelerated growth in the UK.

One of the challenges of a new variant is knowing what to call it. Public Health England simply called it “Variant of Concern 202012/01”. The Covid-19 Genomics UK Consortium, which detected the variant, called it “B.1.1.7” because it mutated from the existing European “B.1.1” line of the Sars-Cov-2 virus. . The Nextstrain virus tracking platform dubbed it 501Y.V1, after one of the mutations it had detected.

Shortly after 501Y.V1 was reviewed in the UK, another variant – now known as 501Y.V2 – became a concern in South Africa. As the name suggests, it has shared some mutations with its UK-based parent, in particular a change in the ‘spike’ protein which can help the virus cling to cells more easily. There were also some differences. While 501Y.V1 appears to be more easily transmitted in the UK, early data suggests that immunity to a previous infection or vaccination should protect against it. In contrast, 501Y.V2 has a mutation that makes it better at avoiding immune responses in laboratory studies. It does this by altering the appearance of the virus, essentially giving a familiar intruder a new disguise.

As 501Y.V2 has become dominant in South Africa, cases and deaths have increased. This despite evidence of considerable antibody levels after the epidemic wave of 2020 and the coming summer months in the country.

There has been a similar startling resurgence of cases in Manaus, Brazil. A recent analysis of antibody levels in blood donors suggests that the majority of the population was infected in 2020. Yet, at the start of 2021, hospitalizations and deaths increased again. This coincided with the detection of a third variant concerning, 501Y.V3, which shares similarities with that of South Africa. As of mid-December, almost half of the Sars-Cov-2 viruses analyzed in Manaus were 501Y.V3.

There have also been new outbreaks in parts of Colombia and Peru that have substantial antibody levels from previous waves, suggesting new variants are circulating there as well. Even if they don’t cause more serious illness in individuals, increased transmission could mean many more cases – and therefore hospitalizations and deaths.

The emergence of three new variants with common characteristics raises the possibility of “convergent evolution”, with viruses independently adapting to human populations around the world in similar ways. The numerous mutations in some of these variants – 23 for 501Y.V1 in the UK – suggest that they may have emerged in an immunocompromised patient; chronic infections can make viruses more likely to adapt than in a patient who recovers quickly.

So where could all of this lead? For viruses like HIV, there is evidence that evolution can eventually lead to less severe variants, as a virus that kills hosts quickly may not spread as easily as a virus that causes a milder infection. Since transmission of Sars-Cov-2 tends to occur early in an infection, before a person becomes seriously ill, it is not clear that a less deadly Sars-Cov-2 virus would have a evolutionary advantage over existing variants. However, as epidemics and vaccination campaigns lead to increasing immunity, there could be additional pressures on viruses to evolve. A recent study suggests that seasonal coronaviruses gradually evolve to evade immunity generated in previous years, leading to re-infections over time.

During every outbreak, there is a debate about how to deal with the next threat of disease. But these new variations – and the realization that there may be more out there undetected – suggests that this debate is no longer hypothetical. The new strains must be treated as new threats and countries urgently need to decide how to deal with them.