The more contagious coronavirus variant discovered in Britain has now been detected in more than 50 countries, including Argentina on Saturday, and is believed to be driving surges in at least two.
But how widely that version of the virus has actually spread — and whether it could already be a factor in other countries’ surges — may not be clear for some time, because the necessary genomic testing remains rare. And at least three other troubling variants are spreading less widely, according to available data: one identified in South Africa and two in Brazil.
Britain, one of Europe’s worst-hit countries during the pandemic, leads the world in identifying the exact genetic sequence of virus samples, known as genomic surveillance. That capacity enabled it to put the world on notice with an announcement on Dec. 14 that it had detected the variant scientists call B.1.1.7, along with the disturbing news that it was most likely the cause of skyrocketing infections in London and the surrounding area.
That version of the virus, which has been widely referred to as “the U.K. variant,” though its origin is unknown, has so far left the most evident trail. It is believed to have helped push Ireland’s positivity rate past Britain’s to become the third highest in the world — over just a few weeks.
Antoine Flahault, the director of the Institute of Global Health in Geneva, said the variants were causing concern all over Europe. He said that several countries were now trying to put in effect more frequent and systematic sequencing to get a clearer picture of their impacts.
None of the variants is known to be more deadly or to cause more severe disease, but increased transmissibility adds to caseloads that further strain hospitals and result, inevitably, in more deaths. Their emergence adds to the urgency of mass vaccination campaigns, which have had troubled starts in Europe and the United States; are only beginning in many other countries, like India; and are at minimum months away in many others.
Dr. Emma Hodcroft, a molecular epidemiologist at the University of Bern in Switzerland, said that outside of Britain and Ireland, scientists remained cautious about linking recent surges in Europe to B.1.1.7. “For most of Europe, the expected prevalence of the variant is still under 5 percent — likely too small to be making a big difference in case numbers,” she said.
“We do not need new variants to see increase in cases,” Ms. Hodcroft added. “We’ve seen many, many surges in cases around the world that we can confirm did not seem to be associated with variants.”
The timing of the variant’s spread is a crucial question for countries like Portugal, which has found fewer than 80 cases of B.1.1.7 but has a fragile health care system that could be easily overwhelmed. In the last seven days, its infection rate has been among the world’s highest, with an average of more than 8,800 new infections, or 86 per 100,000 people. On Saturday, the country reported nearly 11,000 cases and 166 deaths, its worst day of the pandemic. The authorities imposed a monthlong lockdown on Friday.
Many countries expect that B.1.1.7’s impact still lies ahead.
That is a disturbing possibility in the United States, which has long had the world’s largest coronavirus outbreak and is in the midst of a post-holiday surge. On Friday, federal health experts warned in dire terms that B.1.1.7 would most likely be the dominant source of infection in the country by March.
Nearly 20 European countries have found B.1.1.7 so far. In Denmark on Saturday, the authorities said more than 250 cases had been detected in samples taken since November. The country’s health minister has predicted that the variant will predominate by mid-February. The country’s coronavirus monitor also reported that it had identified a case of the variant found in South Africa, Reuters reported.
Many countries in Europe are redoubling their efforts at mitigation. A nationwide 6 p.m. curfew went into effect in France on Saturday, and the authorities have warned that they could reimpose strict lockdown measures. Scotland tightened already strict restrictions, including banning drinking outside and barring customers from stepping inside establishments to buy takeaway food or coffee. Britain and Germany have closed schools.
In a stark contrast, the authorities in Spain have refused to impose a new nationwide lockdown, arguing that the recent discovery of dozens of cases of the variant was not to blame for a record surge in infections.
On Saturday, Britain reported eight cases of one of the variants found in Brazil, hours after the British authorities imposed a travel ban from Latin American countries and Portugal, which is linked to Brazil by its colonial history and by current travel and trade ties. Italy also suspended flights from Brazil, its health minister, Roberto Speranza, announced on Facebook.
A leading epidemiologist said that a second variant discovered in Brazil was most likely already present in Britain.
“We are one of the most connected countries in the world, so I would find it unusual if we hadn’t imported some cases into the U.K.,” Professor John Edmunds, a member of a group of scientists advising the government on the pandemic, said about the second variant, which was found in the Brazilian city of Manaus.