A more contagious form of the coronavirus began to circulate in the United States.
In Britain, where it was first identified, the new variant became the predominant form of the coronavirus in just three months, accelerating the nation’s rise and filling its hospitals. It can do the same in the United States, exacerbating a relentless increase in deaths and overburdening the already tense health system, experts warned.
A variant that spreads more easily also means that people will need to adhere religiously to precautions such as social detachment, wearing a mask, hand hygiene and better ventilation – undesirable news for many Americans who are already irritated by restrictions.
“The bottom line is that anything we do to reduce transmission will reduce transmission of any variants, including this one,” said Angela Rasmussen, a virologist affiliated with Georgetown University. But “it may mean that more targeted measures that are not like a total block will not be as effective”.
What does it mean for this variant to be more transmissible? What makes this variant more contagious than previous iterations of the virus? And why should we be concerned with a variant that spreads more easily, but does not seem to make anyone more sick?
We asked experts to evaluate the evolution of research on this new version of the coronavirus.
The new variant seems to spread more easily among people.
Many variants of the coronavirus have emerged since the pandemic began. But all the evidence so far suggests that the new mutant, called B.1.1.7, is more transmissible than the previous forms. It first appeared in September in Britain, but already accounts for more than 60 percent of new cases in London and surrounding areas.
The new variant appears to infect more people than previous versions of the coronavirus, even when the environments are the same. It is unclear what gives the variant this advantage, although there are indications that it can infect cells more efficiently.
It is also difficult to say exactly how much more transmissible the new variant can be, because scientists have not yet done the kind of laboratory experiments needed. Most of the conclusions were drawn from epidemiological observations and “there are as many possible biases in all available data,” warned Muge Cevik, an infectious disease specialist at the University of St. Andrews in Scotland and a scientific adviser to the British government.
Scientists initially estimated that the new variant was 70% more transmissible, but a recent modeling study set that number at 56%. Once the researchers analyze all the data, it is possible that the variant will end up being only 10 to 20 percent more transmissible, said Trevor Bedford, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle.
Still, Bedford said, it is likely to pick up quickly and become the dominant form in the United States in March. Scientists like Dr. Bedford are closely tracking all known variants to detect any additional changes that could alter their behavior.
In addition to greater transmissibility, the variant behaves like previous versions.
The new mutant virus can spread more easily, but in all other respects, it looks little different from its predecessors.
So far, at least, the variant does not seem to make people sicker or lead to more deaths. Still, there is cause for concern: a more communicable variant will increase the number of deaths simply because it will spread more quickly and infect more people.
“In that sense, it’s just a numbers game,” said Rasmussen. The effect will be amplified “in places like the US and the UK, where the healthcare system is really at its breaking point”.
The transmission routes – through large droplets and small and tiny aerosolized particles adrift in crowded indoor spaces – have not changed. This means that masks, limiting time with other people and improving ventilation in indoor spaces will help to stem the spread of the variant, as these measures do with other variants of the virus.
“By minimizing your exposure to any virus, you will reduce the risk of being infected, and this will reduce transmission in general,” said Dr. Rasmussen.
Infection with the new variant can increase the amount of viruses in the body.
Some preliminary evidence from Britain suggests that people infected with the new variant tend to carry higher amounts of the virus in their noses and throats than those infected with previous versions.
“We are talking in a range between 10 times greater and 10,000 times greater,” said Michael Kidd, a clinical virologist at Public Health England and a clinical consultant to the British government who studied the phenomenon.
There are other explanations for the finding – Dr. Kidd and his colleagues did not have access to information about when people were tested for the disease, for example, which could affect their so-called viral loads.
Still, the discovery offers a possible explanation as to why the new variant spreads more easily. The more viruses infected people harbor in their noses and throats, the more they are expelled into the air and surfaces when they breathe, speak, sing, cough or sneeze.
As a result, situations that expose people to the virus are more likely to spread new infections. Some new data indicates that people infected with the new variant spread the virus to more contacts.
With previous versions of the virus, contact tracking suggested that about 10 percent of people who have close contact with an infected person – less than two meters for at least 15 minutes – inhaled enough viruses to be infected.
“With the variant, we can expect 15 percent of them,” said Dr. Bedford. “Today, risky activities are becoming more risky.”
Scientists are still learning how mutations have changed the virus.
The variant has 23 mutations, compared to the version that broke out in Wuhan, China, a year ago. But 17 of those mutations appeared suddenly, after the virus diverged from its most recent ancestor.
Each infected person is a melting pot, offering opportunities for the virus to mutate as it multiplies. With more than 83 million people infected worldwide, the coronavirus is accumulating mutations faster than scientists expected at the beginning of the pandemic.
The vast majority of mutations do not provide any advantage to the virus and disappear. But mutations that improve the virus’s ability or transmissibility have a greater chance of catching it.
At least one of the 17 new mutations in the variant contributes to its greater contagiousness. The mechanism is not yet known. Some data suggest that the new variant may bind more strongly to a protein on the surface of human cells, allowing it to infect them more quickly.
It is possible that the variant will flourish in the nose and throat of an infected person, but not in the lungs, for example – which may explain why patients spread more easily, but do not develop more serious illnesses than those caused by previous versions of the virus. Some flu viruses behave similarly, experts noted.
“We need to look at this evidence as preliminary and cumulative,” said Cevik of the growing data on the new variant.
Still, research so far suggests an urgent need to reduce transmission of the variant, she added: “We need to be much more careful with everything and look for gaps in our mitigation measures.”