LONDON — Britain reported 78,610 new coronavirus cases on Wednesday, the best variety of infections in a single day for the reason that begin of the pandemic, and stark affirmation that the Omicron variant is rampaging throughout the nation.

New circumstances spiked by a 3rd since Tuesday; the quantity is greater than 10,000 increased than the earlier worst day for infections, Jan. 8, when the Alpha variant was ravaging the nation. The seven-day common of recent circumstances is 65,008, a 19.1 p.c enhance over the earlier seven-day interval. Officers didn’t specify what share of the brand new circumstances could be Omicron, although they stated a majority in London had been from the variant.

Chris Whitty, the chief medical officer for England, warned that additional data could be damaged in coming days, with the Omicron variant doubling at a charge of lower than each two days in components of the nation. Whereas the impact on hospitalization and mortality charges stays unclear, he warned that Britain’s Nationwide Well being Service would face a deluge of sufferers just because the expansion in circumstances was so explosive.

“It is a actually critical risk,” Dr. Whitty stated at a information convention, alongside Prime Minister Boris Johnson and the medical director of major look after N.H.S. England, Nikki Kanani. “It’s transferring at a fully phenomenal tempo.”

Mr. Johnson redoubled his marketing campaign for individuals to get vaccine booster pictures. About 650,000 individuals obtained pictures on Tuesday, one other record-breaking day. Mr. Johnson has set a aim of delivering boosters to all adults by the top of the month, a goal that will require administering greater than 1 million pictures a day.

Whereas Mr. Johnson didn’t announce any extra restrictions on Wednesday, he urged the general public to be even handed in socializing through the holidays. Parliament on Tuesday passed the government’s plan to impose a system of vaccine certification to enter nightclubs and enormous indoor venues, although practically 100 members of Mr. Johnson’s Conservative Get together voted in opposition to the measure.

“We’re not canceling individuals’s events,” Mr. Johnson stated. “What we’re saying is, consider carefully earlier than you go.”

The prime minister has been beneath fierce political strain in latest weeks after experiences that his workers held vacation gatherings at Downing Avenue final 12 months, at a time when the federal government was instructing individuals to not meet with associates and even members of the family. A report on these allegations is predicted to be launched in coming days, and Mr. Johnson stated he welcomed the investigation.

Whereas there’s preliminary proof from South Africa that the Omicron variant is much less extreme than earlier variants, Dr. Whitty cautioned in opposition to over-interpreting the info.

In Britain, 774 individuals had been admitted to hospitals on Wednesday, a ten.4 p.c enhance over the past seven-day interval, whereas 165 individuals died, a 5 p.c decline over the seven earlier days.

Omicron’s unfold has been notably dramatic in London, the place the vaccination charge is decrease than different components of the nation. The prime minister stated hospitalization charges in London had been up by a 3rd.

“We’ve obtained two epidemics on prime of one another,” Dr. Whitty stated, “a flat Delta epidemic and a quickly rising Omicron epidemic.”