With cases of the omicron variant doubling every three days and the government doing an about-face on restrictions it had long resisted, Britain is bracing for a new coronavirus surge, unsure if it will be a relatively minor event or a return to the dark days of earlier pandemic waves.

So far, the number of omicron cases — 817 confirmed by Thursday, though officials say the real figure is likely much higher — is small compared with the daily average of 48,000 new coronavirus cases overall. But the government’s Health Security Agency warned that if the recent growth rate continues, “we expect to see at least 50 per cent of Covid-19 cases to be caused by the omicron variant in the next two to four weeks”.

Early evidence in Britain backs up tentative findings elsewhere, notably in South Africa, where the heavily mutated new variant is already widespread: It appears to be the most contagious form of the virus yet, a previous case of Covid-19 provides little immunity to it, and vaccines seem less effective against it.

But it also seems to cause less severe illness than earlier variants.

Britain’s experience with omicron may be a harbinger of what others can expect. Until now, it has been looser about social restrictions than many other nations in western Europe, and Britain ordinarily has extensive travel to and from South Africa, so it could be the first wealthy country to be hit hard by omicron.

It also has one of the world’s most robust systems for sequencing viral genomes, so it can identify and track new variants earlier and more thoroughly than other countries. “I think we are looking at a horrible winter,” said Peter English, a retired consultant in communicable disease control.

New York Times News Service