IN BRITAIN

Medical evidence links increase in deaths to coronavirus mutation.

There is some evidence a new coronavirus variant first identified in southeast England carries a higher risk of death than the original strain, the British government’s chief scientific adviser said Friday — though he stressed the data is uncertain.

LONDON — Prime Minister Boris Johnson said Friday a new variant of the coronavirus, first detected in England and now spreading around the world, including in the United States, “may be associated with a higher degree of mortality.”

The new strain of the virus was already known to be far more infectious than the original coronavirus. Some studies have suggested it is 50% to 70% more transmissible.

But at a news briefing at Downing Street on Friday, Johnson and his advisers gave the first indication that the strain may also be more deadly.

England’s chief scientific adviser, Patrick Valance, gave an example.he said that among 1,000 men in England 60 years or older, the original virus would kill 10. The new variant, he said, would kill 13 or 14.

Since the new variant was discovered in Britain last year, public health officials have stressed that the mutation did not appear to make people sicker or increase deaths. So this small but measurable uptick in mortality is potentially worrisome.

The prime minister and his science adviser repeated that current evidence shows existing vaccines remain effective against the original virus and new variants.

The coro navirus, l ike all viruses, is replicating and changing all the time — with errors and mutations in its genetic material.

Most of those mutations are not important, but some could lead a virus to become more or less infectious, or make people more or less sick.

In addition to the so-called “U.K. variant,” new mutations discovered in South Africa and Brazil are being watched closely.

LEON NEAL/POOL VIA AP At a news conference Friday, British Prime Minister Boris Johnson said the new variant of the coronavirus, which was first discovered in the south of England, may be linked with an increase in the mortality rate.