The author, an epidemiologist at the London School of Hygiene and Tropical Medicine, is the author of ‘The Rules of Contagion’
During every major epidemic I have worked on, there are speculations about virus mutations. These mutations are mostly harmless, just random errors in the genetic code of a virus that do not change how it infects or spreads. But every now and then a collection of mutations emerges that dramatically changes the threat we face. In recent weeks, researchers have noticed three worrying new Sars-Cov-2 variants that are spread among the various virus lines that are spreading worldwide. Such variants could change the form of the pandemic in 2021.
The first new variant was detected in the east of England in the autumn of 2020. It sparked concern after spreading easily, despite the controls introduced in November, which surpassed the existing variants to become dominant in large parts of the UK by the end of December. Early analysis of contact detection data and local epidemic growth suggested that this variant may be 40 to 70 percent more transmissible than earlier viruses. It has since been detected in other countries, with initial patterns in Denmark and Ireland corresponding to the accelerated growth in the UK.
One of the challenges with a new variant is how to name it. Public Health England simply calls 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 was mutated from the existing ‘B.1.1’ European generation of Sars-Cov-2 viruses. The Nextstrain virus detection platform named it 501Y.V1, after one of the mutations it contracted.
Not long after 501Y.V1 came under scrutiny in the United Kingdom, another variant – now known as 501Y.V2 – became a source of concern in South Africa. As the name suggests, it has shared a number of mutations with its family member in the UK, most notably a change in the ‘spike’ protein that could help the virus more easily attach to cells. There were also some differences. While 501Y.V1 appears to transmit more easily in the UK, early data suggest that immunity should protect against past infections or vaccination against them. In contrast, 501Y.V2 has a mutation that makes it better to evade immune responses in laboratory studies. It does this by changing the appearance of the virus, giving a known offender a new disguise.
As 501Y.V2 became dominant in South Africa, cases and deaths increased. This is despite evidence of significant antibody polls following the epidemic in 2020 and the coming summer months in the country.
There was a similar confusing revival of affairs in Manaus, Brazil. Recent analysis of the antibody level among blood donors indicates that the majority of the population will be infected by 2020. Yet hospitalizations and deaths grew again in early 2021. This coincided with the discovery of a third variant, 501Y.V3, which has similarities to those in South Africa. By mid-December, nearly half of the Sars-Cov-2 viruses analyzed in Manaus were 501Y.V3.
There are also new outbreaks in areas in Colombia and Peru with significant antibody surveys of earlier waves, leading to the suspicion that there are new variants as well. Even if they do not cause serious illness to 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 around the world in similar ways. The many mutations in some of these variants – 23 for 501Y.V1 in the UK – suggest that it may have originated in a patient with an immunodeficiency; chronic infections can give viruses more chance to adapt than in a patient who recovers quickly.
Where can all this lead? For viruses such as HIV, there is evidence that evolution may eventually result in less severe variants, since a virus that kills hosts quickly may not spread as easily as one that causes a milder infection. Since the spread of Sars-Cov-2 tends to occur early in an infection, before someone becomes seriously ill, it is not clear that a less deadly Sars-Cov-2 virus would have an evolutionary advantage over existing variants. As epidemics and vaccination campaigns lead to increased immunity, viruses can have additional pressure to develop. One recent study suggests that seasonal coronaviruses gradually evolve to evade immunity generated in previous years, leading to reinfections over time.
During each epidemic, there is a debate about how to tackle the next disease threat. But these new variants – and the realization that there may be more unnoticed – suggest that this debate is no longer hypothetical. The new tribes must be seen as new threats, and countries must urgently decide how to tackle them.