COVID ‘variant soup’ is making winter surges hard to predict

Amid the chaos, patterns are emerging ...

NATURE – Some call it a swarm of variants — others refer to it as variant soup. Whatever it’s called, the current crop of immunity-dodging offshoots of the Omicron variant of SARS-CoV-2 is unprecedented in its diversity.

This complexity makes it harder to predict coming waves of infection. It might even lead to a ‘double wave’ in some places, as first one variant and then another overtakes a population.

But amid the chaos, patterns are emerging. The swarm has helped scientists to pinpoint a handful of immunity-evading mutations that power a variant’s spread. Globally, a few heavyweight variants have emerged, yielding different outcomes in different regions — at least, so far.

In Europe, North America and Africa, the prevalence of Omicron offshoots in the BQ.1 family is rising quickly, even as overall cases seem to fall.

In Asian countries including Singapore, Bangladesh and India, a lineage called XBB has already set off fresh waves of infection. Scientists are closely watching several regions where both are circulating, to see which has the edge.

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“In the end, probably, some variants are going to dominate, but it’s less decisive than it was in the past,” says Cornelius Roemer, a computational biologist at the University of Basel in Switzerland.

One big family

The variants that have driven past waves, such as Alpha and Delta, all arose from distinct branches of the SARS-CoV-2 family tree. But since Omicron emerged in late 2021, it has spawned a series of subvariants, including BA.2 and BA.5, that have sparked global waves of infection.

Many countries put their BA.5-led surges in the rear-view mirror in mid-2022, but most scientists thought it was only a matter of time before another sublineage came to the fore.

For the past few months, variant trackers have been combing through global SARS-CoV-2 sequencing data to identify candidates …


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