The streets of central Glasgow were deserted on January 5 after the United Kingdom imposed a strict blockade to prevent the spread of a new variant of SARS-CoV-2.
ANDY BUCHANAN / AFP via Getty Images
By Kai Kupferschmidt
Science‘s COVID-19 reports are supported by the Pulitzer Center and the Heising-Simons Foundation.
For COVID-19 researchers, the new year brings a strong sense of déjà vu. As in early 2020, the world is anxiously watching a virus spread in one country and trying to analyze the risk for everyone else. This time, it is not a completely new threat, but a rapidly spreading variant of SARS-CoV-2. In southeastern England, where variant B.1.1.7 first caught the attention of scientists last month, it quickly replaced other variants and could be heralding a new and particularly dangerous phase of the pandemic.
“One concern is that B.1.1.7 will now become the dominant global variant with its highest transmission and will drive another very, very bad wave,” said Jeremy Farrar, an infectious disease specialist who runs the Wellcome Trust. Considering that the path of the pandemic in 2020 was quite predictable, “I think we are entering an unpredictable phase now” as a result of the evolution of the virus, said Farrar.
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The concern has prompted some countries to speed up vaccine authorizations or discuss dosing regimes that can quickly protect more people. But as the new variant appears in several countries, many scientists are asking governments to strengthen existing control measures as well. UK Prime Minister Boris Johnson announced new severe restrictions on January 4, including closing schools and asking not to leave their homes unless strictly necessary. But other countries hesitated. “I feel that we are in a different situation now, where much of Europe is sitting and looking,” says virologist Emma Hodcroft, from the University of Basel. “I really hope that this time we can recognize that this is our early warning signal and this is our chance to move forward on this variant.”
In announcing the UK restrictions, Johnson said the new variant is between 50% and 70% more transmissible. But the researchers were careful to point out uncertainties. Cases skyrocketed in the UK in the past month, but the increase came as different parts of the country had different levels of restrictions and amid changes in people’s behavior and regional infection rates in the run up to Christmas – “a complex scenario ”This makes it difficult to identify the effect of the new variant, says evolutionary biologist Oliver Pybus of the University of Oxford.
However, the evidence has rapidly increased that the many mutations in B.1.1.7, including eight in the crucial spike protein, increase spread. “We are relying on several flows of imperfect evidence, but virtually all evidence points in the same direction now,” says Adam Kucharski, modeler at the London School of Hygiene & Tropical Medicine. For example, an analysis by Public Health England showed that about 15% of contacts from people infected with B.1.1.7 in England were tested positive, compared with 10% of contacts from people infected with other variants.
If other countries that have detected B.1.1.7 also see its increase, it will be “the strongest evidence we will have”, says Pybus. In Ireland, where infections have also increased rapidly, the variant now accounts for a quarter of the sequenced cases. And data from Denmark, which leads the European Union in sequencing SARS-CoV-2, is also not reassuring. Routine surveillance there detected the variant dozens of times; their frequency went from 0.2% of genomes sequenced in early December to 2.3% 3 weeks later. “We had what appears to be an example of exponentially growing poster child in the past 4 weeks in Denmark,” says genomicist Mads Albertsen, from the University of Aalborg. The numbers are still too low to draw firm conclusions, warns Albertsen, but if the trend continues, it will be a clear sign that many countries may face the same problems as the United Kingdom. “We must start preparing for the fact that this is happening elsewhere,” says Hodcroft.
I really hope that this time we can recognize that this is our initial warning signal and this is our chance to move forward in this variant.
The lack of evidence – so far – that the new variant makes people sicker is little consolation. The increase in the transmissibility of a virus is much more treacherous than the increase in pathogenicity because its effects grow exponentially, says Kucharski. “If you have something that kills 1% of people, but a large number of people get it, it will result in more deaths than something that a small number of people get, but it kills 2% of them.”
If the UK estimates a 50% to 75% increase in the number of virus reproductions, or R, is true, “preventing the virus from spreading has become much more difficult,” says Viola Priesemann, a physicist at the Max Planck Institute for Dynamics and self-organization that have shaped the pandemic and the effects of non-pharmaceutical interventions, such as physical distance and closing schools. “In Germany, you would need two additional large measures to keep the reproduction number below 1,” says Priesemann.
Isolating patients and tracking, quarantining and testing their contacts is a part of any attempt to do so; these measures alone can reduce R from about 2 to about 1, Priesemann showed for Germany. But that effect wears off when the number of cases reaches a critical threshold and public health officials are overwhelmed, which means that tougher measures can now help stem the spread of the new variant later. “This is yet another reason to choose very low numbers,” says Priesemann, who co-authored a letter from December 2020 to The Lancet urging Europe to adopt a joint strategy to rapidly reduce infections. Hodcroft agrees. “The case has never been stronger,” she says. “What is the worst case here? We exceed and obtain cases so low that we can get rid of a series of restrictions. “
Dramatically reducing infections has the added benefit of reducing the chances of the virus evolving further. Other variants have already emerged, notably a so-called 501Y.V2 in South Africa, which are as worrying as B.1.1.7, adds Farrar. “It is essentially a numbers game: the more viruses circulate, the more chances that mutants will appear,” he says. In the long run, mutations may appear that threaten the effectiveness of vaccines.
It is disheartening to feel that the world is back to what it was in early 2020, says epidemiologist William Hanage of the Harvard TH Chan School of Public Health. “But we have to stop this virus. … Fatalism is not a non-pharmaceutical intervention. “