News Desk :
VIROLOGISTS WILL tell you that predicting how a new virus might evolve is a fool’s errand. Predicting that it will evolve, though, is money in the bank. The virus that causes covid-19, SARS-CoV-2, is no exception. Since the first copy of its genome was published on January 10th 2020, sequenced from a sample collected in Wuhan days earlier, some 5.6m SARS-CoV-2 genomes have been added to GISAID, a database. They have been arranged into 23 clades-groupings with a distinct common ancestor which differ from the original sequence and from all the others in at least one particular. Each clade has had the chance to outcompete the other versions, and almost all have failed. Most differences do not make much of a difference. Then again, some do-spectacularly so.
Between November 15th and 25th the number of new cases of covid in South Africa jumped from fewer than 400 a day to more than 2,000. Sequencing showed that a large number of these were down to a variant initially known as B.1.1.529, and subsequently designated Omicron. In genomic terms, Omicron is wildly different from any other variant seen to date.
The nature of its differences suggested, in theory, that it might be better at getting into human cells than its relatives were. It might also be better at avoiding the attentions of antibodies from vaccination or an earlier infection. Virologists had long thought that a variant which combined both those advantages “would be a pretty dangerous thing”, according to Noubar Afeyan, a co-founder of Moderna, one of the manufacturers of mRNA vaccines against SARS-CoV-2. But they also thought it was unlikely. Now “Omicron is exactly that”, Mr Afeyan says. Its mutations and its apparently rapid spread added up to something potentially scary.
On November 26th the World Health Organisation (WHO) accordingly labelled Omicron a “variant of concern”, the fifth version of the virus to be thus marked out. Stockmarkets around the world fell sharply on the news. Companies sensitive to covid restrictions, such as airlines and hotel chains, were hit hard. The dollar, a safe-haven investment in times of uncertainty, has strengthened. But this was not a shock on anything like the scale of that seen during the initial spread of the disease.
The WHO has warned that the new strain carries a “very high” risk of causing surges in infection all around the world. As yet, though, such a surge has been seen only in South Africa, and things may stay that way. It is possible that the surge had other causes and that any variant around at the time would have spread. Or some factor which favours the variant in South Africa may be absent everywhere else.
There is precedent for this. Southern Africa suffered a wave of the Beta variant at the end of 2020, but it never became established elsewhere. Alpha swept across Europe but never became established in southern Africa. The reasons a variant spreads in one place and not another are, like much of the rest of evolution, thought to be largely environmental. For SARS-CoV-2 a crucial part of the environment is the immune system, and immune systems are different all over the world. How different genes, endemic infections, general levels of health, microbiomes and more end up stopping one variant from displacing another is largely uncharted territory.
But not all variants stay local. First detected in India roughly a year ago, Delta displayed a level of transmissibility which saw it outcompete other strains almost everywhere, establishing itself as the dominant strain and often causing new waves of disease as it did so.
It is the possibility that Omicron might now outcompete Delta-either through being inherently more transmissible, by being better at overcoming prior immunity, or a bit of both-that has the world on edge and may yet see markets lose their cool. Many countries have banned or restricted travel from southern Africa. Some, like Israel and Japan, have banned all foreigners from coming in. Despite this, by December 2nd over two dozen countries had reported the presence of the Omicron variant within their borders (see map). That seems to suggest the cat is already out of the bag; if Omicron has the ability to displace Delta, it is probably already in a position to do so.
Courtesy: The Economist
