The World Health Organization (WHO) has announced that the B.1.1.529 line of Sars-CoV-2, which is believed to have surfaced in southern Africa, will be designated as a Concerning Variant (VoC) named omicron target. This decision has already resulted in a widespread shift in priorities in pandemic management at the global level.

The WHO has recommended increased surveillance, particularly virus genome sequencing, among other things; specific research to understand the dangers of this variant; and ramping up mitigation measures such as B. wearing masks. In the UK and many other countries, stricter restrictions on international travel have already come into effect. In fact, Japan has closed its borders to all foreign visitors.

The speed at which the omicron variant was referred to as VoC was staggering. A little more than two weeks have passed since the first known infections in Botswana and South Africa. Compare this to the delta variant that is currently prevalent in Europe and many other parts of the world. This variant was first reported in India in October 2020, but while it caused a huge spike in cases in the country (and spread to many others) it wasn’t given elevated status from VoC until at least six months later.

The danger posed by the Delta has certainly been sluggish, and lessons have undoubtedly been learned of the importance of acting quickly to nip dangerous new varieties in the bud, or at least to slow their spread, in order to buy the world some time. But that delay also reflected the difficulty in providing robust evidence of what a new variant is capable of.

There are three types of behavior (“phenotypes”) that determine the threat posed by a new variant. These are transmissibility (the rate at which it is transmitted from one person to another), virulence (the severity of the symptoms of the disease), and immune evasion (the level of protection a person receives from the vaccine or a natural infection). The underlying genetic and evolutionary interactions between these three phenotypes are complex, and to uncover them requires both detailed clinical and epidemiological data from the real world and careful laboratory experimentation.

So what made the Omicron variant of the WHO and many experts around the world so concerned about so little data – and are their warnings that it is “the most worrying we have ever seen” justified? ?

There is still no evidence that Omicron causes any more serious illness, but almost no data is available. It remains to be seen whether anecdotal reports from South Africa, which suggest that this variant causes milder symptoms, will prove to be true, particularly in older or otherwise vulnerable people. However, there is clear cause for concern in terms of both portability and immune evasion.

The increased transferability of a new variant can be difficult to determine because stochastic (random) effects can lead to alarming increases in the number of cases without an underlying change in viral genetics being necessary. When case numbers are relatively low, as was the case recently in South Africa, super-spreading or “charter” events can happen to lead to a dramatic increase in the prevalence of individual lineages.

Despite these caveats, the consensus is that the Omicron variant is likely to spread faster than other variants. In South Africa’s Gauteng province, the advent of Omicron is said to have raised the R-number (the average number of people an infected person will pass a virus to) from about 1.5 to nearly 2, a significant shift if true. Unsurprisingly, it is also being taken up in more and more countries outside of southern Africa, including the UK, Israel, Belgium, Canada, Australia, the Netherlands, and Austria.

Jaw down

By far the most stunning feature of the Omicron variant, however, is the fact that it represents a significant and sudden evolutionary leap, which is reflected in the unprecedented number of mutations in the genome. How this came about is still speculated, but crucially, 32 mutations affected the spike protein, many of which are known to alter the way the virus interacts with the antibodies produced by the vaccines or a previous infection.

It is this potential for increased immune defense combined with a rapid rate of spread that is so much cause for concern. But predicting how a virus is likely to behave based on genome sequence alone is not an exact science. And there is no clear link between the number of mutations a variant contains and the dangers it can bring.

While the Omicron variant certainly warrants mitigating measures, close monitoring and global research, it is too early to say exactly what we are up against. A clearer picture should emerge in the coming weeks as the evidence builds up.

In the meantime, the world should be grateful for the vigilance and openness of South African and Botswana scientists and public health officials, and the advent of this variant should be a wake-up call to double our efforts for equitable and expeditious vaccine delivery on a global scale.

Ed Feil, Professor of Microbial Evolution at the Milner Center for Evolution, University of Bath

This article was republished by The Conversation under a Creative Commons license. Read the original article.


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