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As horrific as the U.S. Covid-19 outbreak looks right now, it is almost certainly about to get worse.

They’ve raced through South Africa, the United Kingdom, and, increasingly, elsewhere, and now, new, more infectious variants of the coronavirus have gained toeholds in the United States. If they take off here — which, with their transmission advantages, they will, unless Americans rapidly put a brake on their spread — it will detonate something of a bomb in the already deep, deep hole the country must dig out of to end the crisis.

In other countries, scientists fear the variants will reignite outbreaks in places where the virus has already been tamped down. But in the U.S. — which averaged more than 250,000 new infections every day in the last week and where more than 4,000 people are dying some days from Covid-19 — the variants could accelerate what’s already exponential spread in certain areas, and make reining in the U.S. epidemic all the more difficult.


“I’m very, very concerned that we’ve now gone from a virus that we could control to a virus that we really can’t, unless we do something very dramatic,” said Kristian Andersen, an infectious diseases expert at Scripps Research Institute.

A spike in infections — on top of the existing caseloads — could force hospital leaders to consider how to surge capacity, staff, and resources — and weigh what happens if they have too many patients to care for. It could force schools to close again or delay plans to reopen. The variants are also ramping up the pressure on the country’s sputtering vaccine rollout, to try to protect more people and snuff out transmission before the variants become dominant.


Epidemiologists stress the country still has a chance to contain the variants before they become widespread, but only if public health authorities can keep ahead of them. It would require an expansion of testing and genomic sequencing to identify where the variants are starting to spread, and prioritizing contact tracing and quarantining programs to sever chains of transmission. Americans would need to redouble their efforts to wear masks, physical distance, and avoid gatherings. It would be no small feat: The variants loom at a time when health departments are exhausted and stretched thin, and many people are weary of Covid-19 precautions.

Just as the arrival of vaccines was providing a light at the end of a tunnel, “this is like a last-minute twist that creates more problems,” said Northeastern University’s Alessandro Vespignani, who models how emerging diseases spread.

SARS-CoV-2, the coronavirus that causes Covid-19, has been mutating throughout the pandemic, just like any virus. But at least two variants have set off global alarms in recent weeks because of a building body of evidence that they are more contagious than earlier forms of the virus. One, called 501Y.V2 or B.1.351, was first identified in South Africa and has since been found in a dozen or so other countries. The other, B.1.1.7, was first seen in the U.K. and is in more than 30 other countries. The latter is drawing more attention in the U.S. now as more states confirm cases — Indiana, Maryland, and Connecticut among them in this last week — but experts caution B.1.351 could very likely be here as well and could pose just as much of a threat, as could some other emerging variant.

The chart shows the dramatic increase in new Covid-19 cases in the U.K. and in Ireland, where the B.1.1.7 variant has taken off. Screenshot via Our World in Data

The variants at this point do not seem to cause more or less severe cases of Covid-19. But that belies how dangerous a more transmissible variant is, said Maia Majumder, a computational epidemiologist at Boston Children’s Hospital.

“Even if B.1.1.7 (or some other more transmissible variant) isn’t any more likely to cause severe disease or death, we may see a larger volume of deaths in its presence simply because there will likely be more infections than there would be without it,” she wrote in an email.

Ayan Sen, the chair of critical care medicine at the Mayo Clinic in Arizona — which has already had to surge care to handle its current Covid-19 patient load — said it was hard to predict what impact the variants could have on hospitals. But if they led to another increase in patients above where the health system was now, it would require building out more ICU space, and “it would certainly affect patients who need care for reasons other than Covid — surgery, or cancer. It has a domino effect.”

It could also precipitate further considerations about triaging care. “We’re hoping for the best so we don’t have to make decisions about the scarce allocation of resources,” Sen said. “It’s really challenging for us as clinicians who want to do their best for all their patients, when they have to make decisions like that.”

If there was already an urgency to vaccinate people as widely and quickly as possible, the arrival of the variants adds accelerant. In order to bring the U.S. epidemic to a close, the population needs to develop what’s known as herd immunity — and based on transmission dynamics, getting to that point with a faster-spreading virus will require even more people to be vaccinated.

Epidemiologists hope that enhanced mitigation efforts — whether targeted at coronavirus transmission generally or the variants more specifically — could buy the country time to expand its vaccine campaigns before the variants gain too much territory.

“We’re basically in this race, because if we reach herd immunity before B.1.1.7 becomes responsible for a majority of cases, then B.1.1.7 might never become responsible for a majority of cases,” said Brooks Miner, an evolutionary ecologist at Ithaca College.

The U.S. has a notoriously spotty genomic surveillance network for different viral variants, and already, it feels like wherever researchers look for at least B.1.1.7, they’re finding it. Still, experts say that for now, based on available sequencing data, it is still causing just a fraction of new cases. They want to make sure it stays that way.

When more transmissible variants get imported into a country, they don’t immediately take over. It can take weeks or months for them to build up to levels where the impact of their infectiousness starts to be felt, and for them to box out other forms of the virus by spreading faster.

Scientists in the U.K., for example, identified the country had a fast-spreading variant in December, but looked back and noticed B.1.1.7 first appeared in their sequencing data in September. In Ireland, where transmission is among the highest in the world now, B.1.1.7 accounted for 8.6% of sequenced cases one week, then 12.8% the following week, then 24.9%. Now it’s making up roughly half of cases.

Such data suggest that if countries respond quickly, they can hem in the variants before they take off. But there are at least two challenges for the U.S. Because the coronavirus is spreading so easily here in general, more transmissible variants that arrive will “find fertile ground to transmit and generate a lot of cases and eventually replace” older variants, Vespignani said.

Plus, because of the lack of surveillance, it’s not totally clear where in the building-up process the variants are in this country.

“We don’t know what our current position is,” said infectious diseases epidemiologist Caitlin Rivers of the Johns Hopkins Center for Health Security. “Are we on Week 1, or are we on Week 6 and we just haven’t noticed?”

Just how infectious the variants are isn’t totally clear; it can be difficult to disentangle what factors — viral evolution, easing of mitigation policies, people gathering — are contributing to new cases. But some estimates have pegged B.1.1.7 to be 30% to 50% more transmissible than other forms of SARS-2.

The virus still transmits the same way — with people “shedding” it as they breathe or talk or laugh or sing, and others inhaling it into their noses or throats — so at the individual level, the precautions people should take are what UCSF epidemiologist Kirsten Bibbins-Domingo called “all the unglamorous things we have to do, like mask and separate.” It’s not certain whether quick, essential errands pose a greater risk to people because of the variants, and if so, to what extent, but some experts have started calling for the public to wear more masks that are more protective than cloth coverings.

It’s at the population level that the higher transmissibility rate becomes clear. If, say, 60% of people wearing masks could keep a brake on transmission of earlier forms of the virus, then perhaps 80% of people now need to wear masks to have the same benefit. Data from the U.K. show that 15% of contacts of people who had B.1.1.7 contracted the virus, versus 10% of contacts of people with other forms of the virus.

“The rates of transmission are going to be significantly more challenging to contain if we see more widespread proliferation of B.1.1.7,” said Mark Ghaly, the health secretary in California, which has already ordered people in some regions to largely stay at home because local outbreaks have threatened hospital capacity.

In the U.K., B.1.1.7 continued to spread while much of the country was under restrictive policies, with nonessential shops closed and people told to avoid mixing with other households. It resulted in case numbers that threatened hospital capacity, so the country instituted an even stricter lockdown this month. While it remains early, some data show cases in the country are starting to trickle down.

But what that signals is it may take the most extreme policies to rein in the variants if they’re given a chance to run rampant, at a time when U.S. politicians and the public seem done with new restrictions.

As scientists watch the variants build up in other countries, they see it as a preview of what could happen in this country without further action. In a way, it’s reminiscent of how the U.S. dawdled as the initial wave of Covid-19 cases surged into the country last year, not absorbing that a virus that tore through China and then Italy was on its way to doing the same in the U.S.

“I do see some parallels with this point last year,” Rivers said. “We knew there was a concerning situation abroad, and it was fairly easy to imagine it would be relevant to us, and we didn’t lean in at that point.” Seeing the variants drive up cases in other countries, Rivers said, “I worry we can expect the same challenges here.”

Usha Lee McFarling, Helen Branswell, and Eric Boodman contributed reporting.

  • Miroslav Radman prof.dr. sc. is a world-renowned scientist and molecular biologist. Croatian biologist and member of the French Academy of Sciences, European Academy of Sciences and Arts, World Academy of Sciences and European Molecular Biology Organization (EMBO).

    He said very little could be predicted given the spread of COVID-19. People are smart enough not to predict because we don’t have elements to predict the future, ”he said in response to a question about whether today’s figures could have been predicted.“ The most important piece of information is what the consequences of these infections are. Most are asymptomatic and mortality drops sharply over time, so there is no need to panic. It would be good to know why mortality is declining, not just because younger people are getting infected, especially during the summer. It is an interesting observation that mortality is falling sharply compared to February and March, ”Radman said.

    “Imagine a scientific council or I personally saying,‘ Just relax, pretend like nothing’s happening ’and then be 100.00 dead.You can’t speak against that precautionary principle because every life is precious. But on the other hand, roughly one percent of the population dies every year if there is no war or some terrible epidemic.One percent is born and that is your life.It dies and is born, and it is up to the people responsible for public health to make sure that as few people as possible die too they do their job very well, ”Radman pointed out. In conclusion, he shared some of his thoughts, as a geneticist, on what could happen to the virus.

    “And scientists when they don’t have data can’t be functional scientists if they don’t have data. I, as a geneticist, predict that a virus will become extinct by accumulating mutations, its own copying errors, because those viruses that have RNA rather than DNA as a genome mutate about 100,000 times more. The virus may become extinct from genetic death if it accumulates so many mutational errors. And I predict that because we have no data for a future that is by definition unknown, “Miroslav Radman said.

    Miroslav Radman, received the Legion of Honor at the Mediterranean Institute for Life Research (MedILS).

  • “…some estimates have pegged B.1.1.7 to be 30% to 50% more transmissible than other forms of SARS-2.”

    Do the viral-laden “particles” survive longer as they are released? Or has fomite transmission become more of a factor?

    I am desperate to find out more, because I’m the sole caregiver for my mother, who is 77 and has cancer.

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