Omicron appears to be spreading faster in the UK than in South Africa, experts say

• The Omicron variant appears to be spreading faster in the UK than in South Africa, experts say.
• COVID-19 cases caused by Omicron are on course to hit 64,000 a day by Christmas, one expert estimated.

The Omicron variant of the coronavirus appears to be spreading faster in the UK than in South Africa, according to two infectious diseases experts.

COVID-19 cases caused by Omicron are doubling every 2.2 days in the UK, compared with every 3 days in South Africa, Trevor Bedford, associate professor in biostatistics, bioinformatics, and epidemiology at the Fred Hutchinson Cancer Research Center, said on Twitter Wednesday.

Omicron, which emerged in southern Africa in November, spread rapidly in South Africa to become the most common cause of new COVID-19 cases in fewer than two weeks.

Bedford said seasonality may be "more favourable" for Omicron's spread in the UK compared with South Africa, where the climate is warmer.

Professor John Edmunds, of the London School of Hygiene and Tropical Medicine, said in a Webinar hosted by the Royal Society of Medicine Thursday that the spread of Omicron "might even be slightly faster" in the UK than in South Africa. The rate of spread in the UK was "really quite alarming," he said.

Edmunds estimated that UK Omicron cases would hit 64,000 a day in two weeks's time if the virus spread at the current rate. This would be in addition to infections caused by the Delta variant.

"Let's say 1,000 infections today, and in a week's time, you've got 8,000. And in two weeks time, you've got 64,000," Edmunds said. "We may well have really significant numbers of cases of this virus by Christmas."

Edmunds said it was "extremely likely" there were "much more" cases in the community than reported.

The UK has recorded 817 Omicron cases, according to UK Health Security Agency data published Thursday. The agency said in a statement Wednesday that it expected Omicron to become the most common cause of COVID-19 in the UK within two to three weeks.

The Omicron variant has 32 mutations in the "spike protein" – the part of the virus that attaches to cells and is the target for antibodies produced by infections and vaccines. Scientists can't yet say conclusively whether the virus is inherently more infectious, how deadly it is, or how well existing vaccines will protect against it.

Experts have predicted that existing COVID-19 vaccines, particularly after an extra booster dose, should protect against severe COVID-19 caused by Omicron.

Early data from South Africa indicated the rapid spread of Omicron was down to its ability to partially evade the immune response from previous infection.

Bedford said initial infections seeded by travelers spread fast but the rate of spread tended to slow as the virus progressed through communities. He said he expected the spread of Omicron in the UK to slow and "become closer to what's currently observed in South Africa" but cautioned a "significant Omicron wave" was "inevitable."