England's top medical officer announced Saturday that the UK had identified a new variant of the coronavirus that "can spread faster" than previous strains of the virus, prompting Prime Minister Boris Johnson to impose new restrictions on parts of the nation to control its spread.
"We learn from this over time, but we already know enough, more than enough, to be sure that we need to act now," Johnson said during a press conference on Saturday setting new restrictions on London and other parts of England before the Christmas holidays.
"If the virus changes its method of attack, we'll have to change our method of defense," said Johnson.
The UK government announced the new strain of coronavirus on Monday after cases increased in the south and east of England. According to a statement from Public Health England, just over 1,100 Covid-19 cases had been identified with the new variant by Sunday.
Now it is believed the new strain could be up to 70% more communicable than the original strain of the disease, Johnson said on Saturday, adding that it appears to be fueling the rapid spread of infections. Johnson urged residents not to travel and "stay on-site" to keep the new strain from moving around the country and abroad.
The UK reports around 24,061 new Covid-19 cases daily based on a weekly average, an increase of more than 40% from the previous week, according to a CNBC analysis of data compiled by Johns Hopkins University.
"This is early data that needs to be verified, but it is the best we have right now and we need to respond to information as we have it because it is now spreading very quickly," said Johnson.
Professor Chris Whitty, England's chief medical officer, said at the press conference that "viruses are constantly mutating". Seasonal influenza mutates every year, and other new variants of the coronavirus have already been identified in countries like Spain, according to Public Health England.
What needs to be answered is whether the new strain will transmit more easily, make people sick, and whether it will change the way a person's immune system responds to the virus if they are already infected or vaccinated, Whitty said.
So far, a body of evidence from genetic studies, frequency studies, and laboratory studies suggests that the new strain "has a significant, substantial increase in transmissibility," Whitty said. So far, however, there is no evidence that the new strain causes a higher death rate.
Health officials believe the new variant first appeared in London or Kent in mid-September, and by mid-November it is believed to have caused about 28% of cases in London and other parts of south-east England, Whitty said.
Now those numbers are much higher, he said. In London last week, data suggests the new variant accounts for more than 60% of new cases, Whitty said.
"So that tells us that this new variant is not only moving fast, it also transmits better, it also becomes the dominant variant. It beats everyone else in terms of transmission," he said.
However, there is "no evidence" that it causes more severe illness, more hospitalizations, or "more problems than the other virus," Whitty said. While there are reasons to suspect the new variant might alter a person's immune response to the disease, nothing suggests that it has so far, he said.
"We are currently assuming by all scientists that the vaccine response for this virus should be appropriate," he said. "Obviously this has to be checked in the future and we have to remain vigilant in this regard."
The UK has alerted the World Health Organization and will continue to analyze data on the new strain.