What makes a virus variant spread?
Experts provide answers as mutant strain reaches US
A more contagious form of the corona virus has begun circulating 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 that nation’s surge and filling its hospitals. It may do the same in the United States, exacerbating an unrelenting rise in death sand overwhelming the already strained health care system, expertswarned.
A variant that spreads more easily also means that people will need to religiously adhere to precautions like social distancing, mask-wearing, handhygiene and improved ventilation— unwelcome news to many Americans already chafing against 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 virus expert affiliated with Georgetown University. But “it may mean that the more targeted measures that are not like a full lockdown won’t be as effective.”
What does it mean for this variant tobemore transmissible? Whatmakes this variant more contagious than previous iterations of the virus? And why should we worry about a variant that spreadsmore easily butdoes not seem to make anyone sicker?
We asked experts to weigh in.
The new variant:
Many variants of the coronavirus have cropped up since the pandemic began. But all evidence so far suggests that the new mutant, called
B.1.1.7, is more transmissible than previous forms. It first surfaced in September in Britain but alreadyaccounts for more than 60% of new cases in London and neighboring areas.
The new variant seems to infect more people than earlier version soft he corona virus, even when the environments are the same. It’s not clear what gives the variant this advantage, although there are indications that it may infect cells more efficiently.
It’s also difficult to say exactly how much more transmissible the new variant may be, because scientists have not yet done the kind of lab experiments that are required. Most of the conclusions have been drawn from epidemiological observations, and “there’s so many possi
ble biases in all the available data,” cautionedMuge Cevik, an infectious disease expert at the University of St. Andrews in Scotland.
Scientists initially estimated that the new variant was 70% more transmissible, but a recent modeling study pegged that number at 56%. Once researchers sift through all the data, it’s possible that the variant will turn out to be just 10% to 20% percentmore transmissible, said Trevor Bedford, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle.
Evenso, Bedfordsaid, it is likely to catch on rapidly and become the predominant form in theUnited States by March.
Variant like earlierversions:
The new mutant virus may spread more easily, but in
every other way it seems little different than its predecessors.
The variant does not seem to make people any sicker or lead to more deaths. Still, there is cause for concern: A variant that is more transmissible will increase the death toll simply because it will spread faster and infect more people.
“In that sense, it’s just a numbers game,” Rasmussen said. The effect will be amplified “in places like the U.S. and theU.K., where the healthcare system is really at its breaking point.”
The routes of transmission — by large and small droplets, and tiny aerosolized particles adrift in crowded indoor spaces — have not changed. That means masks, limiting time with others and improving ventilation in indoor
spaces will all help contain thevariant’s spread, as these measures do with other variant soft he virus.
“By minimizing your exposure toany virus, you’re going to reduce your risk of getting infected, and that’s going to reduce transmission overall,” Rasmussen said.
Amount of virus in body:
Some preliminary evidence from Britain suggests that people infected with the new variant tend to carry greateramountsof the virus in their noses and throats than those infected with previous versions.
“We’re talking in the range between 10- fold greater and 10,000-fold greater,” said Michael Kidd, a clinical virologist at Public Health England and a clinical adviser to the British government who has studied the phenomenon.
There are other explanations for the finding— Kidd and his colleagues did not have access to information about when in their illness people were tested, for example, whichcould affect their so-called viral loads.
Still, the finding does offer onepossible explanation for why the new variant spreads more easily. The more virus that infected people harbor in their noses and throats, themore 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 carry a greater chance of seeding new infections. Some new data indicate that people infected with the newvariant spreadthe virus to more of their contacts.