British Prime Minister Boris Johnson said on Dec. 13 that, "at least one patient has now been confirmed to have died with Omicron." (Video: The Washington Post)

LONDON — Prime Minister Boris Johnson said Monday that Britain had registered its first death of a patient with the omicron variant, while U.K. health officials warned that the new version of the coronavirus was spreading at jaw-dropping speed.

“I think the idea that this is somehow a milder version of the virus, that’s something we need to set on one side and just recognize the sheer pace at which it accelerates through the population,” Johnson told reporters during a visit to a vaccination clinic in London. He urged people to quickly increase their protection with a booster shot.