What scientists know about the spread of the coronavirus variant

A more contagious form of the coronavirus has started to circulate in the United States.

In Britain, where it was first identified, the new variant has become the predominant form of the coronavirus in just three months, accelerating the country’s skyrocketing and filling its hospitals. It could do the same in the United States, exacerbating a steady rise in deaths and overwhelming the already strained healthcare system, experts have warned.

A variant that spreads more easily also means people will have to religiously adhere to precautions such as social distancing, wearing masks, hand hygiene and better ventilation – bad news for many Americans who rub themselves in. already to restrictions.

“The bottom line is that anything we do to reduce transmission will reduce transmission of all variants, including this one,” said Angela Rasmussen, an affiliate virologist at Georgetown University. But “it may mean that more targeted measures that don’t look like a full lockdown won’t 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 worry about a variant that spreads more easily but doesn’t seem to make anyone sicker?

We asked experts to weigh in on the evolution of research on this new version of the coronavirus.

Many variants of the coronavirus have appeared since the start of the pandemic. 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 surfaced in September in Britain, but already accounts for more than 60% of new cases in London and neighboring regions.

The new variant appears to infect more people than previous versions of the coronavirus, even when the environments are the same. It is not known what gives the variant this advantage, although there are indications that it could infect cells more efficiently.

It’s also difficult to say exactly how much more transmissible the new variant may be, as scientists have yet to do the kind of lab experiments needed. Most of the conclusions have been drawn from epidemiological observations, and “there is so much possible bias in all the available data,” warned Muge Cevik, an infectious disease specialist at the University of St. Andrews in Scotland and scientific adviser. from the British government. .

Scientists initially estimated the new variant to be 70% more transmissible, but a recent modeling study put the figure at 56%. Once the researchers sift through all of the data, it’s possible the variant will turn out to be only 10-20% more transmissible, said Trevor Bedford, evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle.

Even so, Dr Bedford said, it is likely to spread rapidly and become the predominant form in the United States by March. Scientists like Dr Bedford are closely monitoring all known variants for any additional changes that could alter their behavior.

The new mutant virus can spread more easily, but in all respects it looks little different from its predecessors.

So far, at least, the variant doesn’t seem to make people sicker or lead to more deaths. Still, there is cause for concern: A more transmissible variant will increase the death toll simply because it will spread faster and infect more people.

“In that sense, it’s just a numbers game,” said Dr Rasmussen. The effect will be amplified “in countries like the United States and the United Kingdom, where the health care system is really at its breaking point.”

The routes of transmission – through large and small droplets and tiny aerosol particles drifting into congested indoor spaces – have not changed. This means that masks, limiting time with others, and improving ventilation in indoor spaces will all help contain 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 your risk of getting infected, and this will reduce transmission overall,” said Dr Rasmussen.

Some preliminary evidence from Britain suggests that people infected with the new variant tend to carry greater amounts of the virus in their noses and throats than those infected with previous versions.

“We are talking in the range between 10 times greater and 10,000 times greater,” said Michael Kidd, clinical virologist at Public Health England and clinical adviser to the UK government who has studied the phenomenon.

There are other explanations for the discovery – Dr Kidd and his colleagues have not had access to information on the timing of their illness, for example, which could affect their so-called viral load.

Still, the discovery offers a possible explanation for why the new variant spreads more easily. The more viruses infected people harbor in their nose and throat, the more they expel into the air and onto surfaces when they breathe, talk, sing, cough or sneeze.

As a result, situations that expose people to the virus are more likely to sow new infections. Some new data indicates that people infected with the new variant are spreading the virus to more of their contacts.

With previous versions of the virus, contact tracing suggested that about 10% of people in close contact with an infected person – within six feet for at least 15 minutes – inhaled enough virus to become infected.

“With the variant, we might expect 15 percent of these,” Dr Bedford said. “Currently, risky activities are becoming riskier.”

The variant has 23 mutations, compared to the version that erupted 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, providing the opportunity for the virus to mutate as it multiplies. With more than 83 million people infected worldwide, the coronavirus is amassing mutations faster than scientists expected at the start of the pandemic.

The vast majority of mutations bring no benefit to the virus and die off. But mutations that improve the physical form or transmissibility of the virus are more likely to be felt.

At least one of the variant’s 17 new mutations contributes to its greater contagiousness. The mechanism is not yet known. Some data suggests that the new variant can bind more tightly to a protein on the surface of human cells, allowing it to infect them more easily.

It is possible for the variant to bloom in the nose and throat of an infected person, but not in the lungs, for example – which may explain why patients spread it more easily but do not develop more serious illnesses than those caused. by earlier versions of the virus. Some influenza viruses behave similarly, the experts noted.

“We have to view this evidence as preliminary and accumulating,” said Dr 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 overall and look at the gaps in our mitigation measures.”