British Prime Minister Boris Johnson on Saturday announced a “stay at home” order for London and southeast England to slow a new coronavirus strain that is significantly more infectious.

The new strain of the virus “does appear to be passed on significantly more easily,” Johnson said at a televised briefing. He ordered new restrictions for London and south-eastern England from Sunday, saying that under the new “tier four” rules, “residents in those areas must stay at home” at least until December 30.