LONDON (AP) — British Prime Minister Boris Johnson held emergency talks with his Cabinet on Saturday to discuss strategies to curb the spread of COVID-19 as the government’s scientific advisors said a new variant of the coronavirus was accelerating the spread of infections.

England’s chief medical officer, Chris Whitty, said that based on preliminary modeling data and rapidly rising incidence rates in southern England, a government virus advisory group thinks the new strain can spread more quickly.

There is no current evidence to suggest the new strain, which England's public health agency identified through genomic surveillance., is more deadly or that it affects vaccines and treatments, he added.

“We have alerted the World Health Organization and are continuing to analyze the available data to improve our understanding,” Whitty said in a statement.

Viruses mutate regularly, and scientists have found thousands different of mutations among samples of the virus causing COVID-19. But many of these changes have no effect on how easily the virus spreads or how severe symptoms are.

Even when a variant seems to be showing up more often someplace, it can be purely by chance. Scientists would need to study the genetic changes to see if they are influencing disease spread.

Maria Van Kerkhove, WHO’s technical lead on COVID-19, told reporters after receiving notification from England this week that the U.N. health agency had “no evidence this variant behaves differently” and that it was similar to a variant initially reported among mink in Europe. She said scientists would study the virus strain to see if there might be any difference in how it prompts an immune response in people.

Johnson is expected to announce to announce changes to his country's current infection-prevention restrictions when he holds a news conference later Saturday.

London now has the highest case rates in England, and this week moved under the highest level of coronavirus restrictions in the country’s three-tier alert system. Most of southern England joined the capital in an expansion of Tier 3 rules Saturday, meaning a total of 38 million people — or 68% of England’s population — are living under the toughest rules.

Under the restrictions, people cannot socialize indoors or in most outdoor places, and restaurants and pubs only can offer takeaway service. Shops remain open, however.

The government has said restrictions on socializing will be eased from Dec. 23 to Dec. 27 to allow people to travel and celebrate Christmas with family and friends. The temporary holiday rules allow a maximum of three households to meet in a “Christmas bubble,” though Johnson urged residents to keep their celebrations small and short.

The planned relaxation of rules has raised increasing concerns given that infections are already climbing sharply in many places.

The prime minister held an unscheduled meeting on Friday evening to discuss the latest evidence about the mutant strain with officials. He has refused to rule out the prospect of a third national lockdown for England.

Wales and Northern Ireland, which have their own devolved governments and independent rules for controlling the virus, have already announced fresh lockdowns once Christmas is over.

U.K. officials reported another 28,507 confirmed cases on Friday, and 489 deaths of people within 28 days of testing positive for the virus. The U.K. has Europe’s second-highest COVID-19 death toll, behind Italy.

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