“At a superspreading event, the number of cases transmitted will be disproportionately high compared to general transmission, Dr Karan says.
And the risk of these superspreading events may balloon in the presence of superspreading people, who pass on their infection more widely either by being in contact with more people or emitting more of the virus.
“I tend to think of it as this: the vast majority of people may not infect any other people, and some people in certain situations infect a lot of people,” he says. “One person may infect 10 people, or 15 people or 20 people.”
Research is still being done, Dr Karan says, but early results indicate that coronavirus spread is primarily powered by these supercharged events.
“Different models have looked at this and they suggest that 20% of people account for 80% of spread.”
And while risk profiles will vary widely between similar events, Dr Karan says there are certain factors that should raise a red flag.
“If you have any of the following in combination: indoors, crowded, closed spaces, without any sort of personal protective equipment like masks, which you’re not going to have eating – I think those are all high-risk,” he says.” (A)
“On Jan. 6, pro-Trump rioters stormed into the Capitol building in Washington, D.C. Prior to that, many in the crowd attended a rally put on by the president and gathered outside the Capitol. Many videos and photos of the people at the Capitol have surfaced, often showing people without masks or face coverings and standing in close proximity to others who were also maskless. Some health experts think this riot could be a superspreader event for COVID-19.
Large mass gatherings are not always superspreader events. Many people gathered in 2020 for Black Lives Matter protests safely, some events numbering in the thousands or tens of thousands. At the protests, organizers often encouraged people to wear masks, and people who had mask supplies went through the crowd offering them to those without. Volunteers also gave out hand sanitizer to those who wanted it. Health experts believe there isn’t evidence that the Black Lives Matter events may be superspreader events.
“It certainly could be,” says Tara Smith, a professor of epidemiology at Kent State University, in an email to Changing America. “From what I saw in pictures and video, you had a large congregation of individuals who were in close contact for an extended period of time and almost universally unmasked. I saw many photos of individuals coming and going on buses as well, also unmasked, and hanging out in hotel lobbies.”
The scenes at the Capitol suggest that many of the people there didn’t follow public health guidelines.
“Many rioters were yelling, not wearing masks, and there was little to no social distancing – all actions that allow COVID to easily spread. It is possible that this could be a superspreader event,” says infectious disease epidemiologist Beth Linas in an email to Changing America. “More concerning is that many rioters were not from DC and are likely headed home and could bring COVID with them (and they could have brought it to DC as well).”
“If just a few percentage of them are positive for the virus, this could lead to a considerable amount of spread, as we saw with other events such as the Sturgis rally,” says Smith. The Sturgis rally was a mass motorcycle event that happened over the summer in South Dakota. The event lasted 10 days and led to at least 51 primary cases and 21 secondary cases in nearby Minnesota, according to the Centers for Disease Control and Prevention (CDC). That may not be all the cases related to the Sturgis event as it only represents one state’s data and cases may be underreported.
However, most of the rioters were outdoors, and that may have prevented some disease transmission from occurring.” (B)
“Being outdoors is often seen as inherently safe, but it’s only safer. The vast, stirring outdoor air can more easily disperse any virus-toting respiratory droplets that float or shoot out of an infected person’s face. That’s in contrast to crowded and/or poorly ventilated indoor spaces where there’s less chance that droplets will be whisked away, possibly allowing them to build up to higher concentrations, increasing the risk of infection for those in the space. We still don’t know the exact amount of virus particles it takes to infect a person, but higher concentrations are absolutely riskier.
Still, being outside does not mean the virus can’t spread, particularly when maskless people are packed into a dense, stationary mob. Being outdoors or in a well-ventilated space are but single layers in the multilayered approach necessary to reduce risk of spreading the virus. People, even outdoors, should wear masks, stay physically distanced, avoid crowded areas, and practice good hand hygiene. That certainly wasn’t the case in the Trump rally yesterday, just as it hasn’t been in previous rallies, which have also been associated with mass spreading of the virus…” (C)
“The mob that stormed the Capitol on Wednesday did not just threaten the heart of American democracy. To scientists who watched dismayed as the scenes unfolded on television, the throngs of unmasked intruders who wandered through hallways and into private offices may also have transformed the riot into a super-spreader event…
Three distinct groups — Capitol Police, rioters and members of Congress — “were spending time indoors, without social distancing, for long periods of time,” said Dr. Joshua Barocas, an infectious diseases physician at Boston University. The melee likely was a super-spreader event, he added, “especially given the backdrop of the highly transmissible variants that are circulating.”
Dr. Barocas was referring to a highly contagious new variant of the coronavirus, first identified in Britain. It has been spotted in several U.S. states but may well have spread everywhere in the country, making events like the Capitol riot even more risky, he said.
The idea that members of Congress may have been exposed, amid an already difficult transfer of power, particularly disturbed some scientists. “I am worried not only that it could lead to super-spreading, but also super-spreading to people who are elected officials,” said Dr. Tom Inglesby, director of the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health.
And infected members of Congress and law enforcement could have spread the virus to one another as they sheltered from the violence, he noted.
Rep. Jake LaTurner, Republican of Kansas, announced on Twitter early Thursday morning that he had tested positive for the virus. Mr. LaTurner was cloistered in the chamber with other members of Congress for much of the day.
At least a dozen of the 400 or so lawmakers and staff who were huddling in one committee room refused to wear masks even after being offered one, or wore them improperly below their chins, said Representative Susan Wild, Democrat of Pennsylvania.
They gathered in a committee room that quickly became crowded, making social distancing impossible, she said. Some of the lawmakers were unmasked, and several were shouting: “Tensions were high, and people were yelling at each other.”
“I just started getting really kind of angry, thinking about the holidays just passed, and how so many people did not spend time with their immediate families for fear of spreading,” she added, referring to her unmasked colleagues.
Representative Debbie Dingell, Democrat of Michigan, said the environment made her so nervous she sat on the floor at one point, hoping to duck whatever virus might be floating about. She has asked experts whether the lawmakers present should now quarantine, she said. She was wearing two masks, as she often does.
“I get that they think they have their individual freedoms,” she said of Republican lawmakers who eschewed masks. “It’s a rule for a reason. It’s to protect the common good.”
The risk for members of Congress will depend greatly on ventilation in the room where they sheltered, said Joseph Allen, an expert on buildings quality at the Harvard T.H. Chan School of Public Health in Boston.
“If there is a well-designed secure facility, then it would have great ventilation and filtration,” Dr. Allen said. “If it’s a place where they were just hunkered down wherever they could go that was safe, and it was not a place that was designed like that, then we don’t really know.”
It’s natural in a heart-pounding crisis to disregard risks that seem intangible or theoretical, he and other scientists noted.
“You cannot keep distance if you’re trying to leave a very intense and dangerous situation,” said Seema Lakdawala, an expert in respiratory virus transmission at the University of Pittsburgh. “You’re weighing the risk of your life over the risk of getting a virus at that moment.”
Members of Congress returned to continue the electoral count after the rioters were cleared from the Capitol. Some legislators took off their masks before giving a speech, Dr. Barocas noted, at precisely the time they needed to wear them. Talking at a high volume can expel vast quantities of aerosols, propelling them through an enclosed space.
Scientists have documented infectious aerosols suspended in air nearly 20 feet from an infected person. And a recent study from South Korea found that two people had become infected after spending just five minutes in a restaurant, 15 feet away from an infected patron.” (D)
“As for the lawmakers on the receiving end of the chaos, those involved in the electoral count — already facing a transmission risk by gathering in-person for a symbolic vote — were then cramped together, lying on the floor of the chamber in an attempt to take shelter. Many members of Congress have been vaccinated, but it’s a two-dose vaccine, and it’s unclear how protected people are in between the first and second shot, as well as how long it takes for the vaccine to kick in. Even if vaccinated lawmakers achieved immunity, the health of dozens of staff, reporters, and police was endangered as the chaos ensued.
Representative Susan Wild of Pennsylvania said there were 300 to 400 other evacuees in the holding location where she was placed, about half of whom weren’t wearing masks, despite being offered them. “It’s exactly the kind of situation that we’ve been told by the medical doctors not to be in,”…(E)
“As the pandemic has evolved, infectious disease experts have zeroed in on so-called superspreaders who are thought to play a major and disproportionate role in transmitting the virus.
Although pieces of the puzzle are still missing, understanding those broader patterns of transmission will help scientists pinpoint not only how the virus spreads, but also what public health strategies will be most effective to curb runaway outbreaks.
There is no official definition for superspreader events, but they are characterized by incidents that result in large clusters of infections. In March, a Biogen corporate meeting in Boston is thought to have been linked to 20,000 Covid-19 cases, according to a study published to the preprint server medRxiv that has yet to be peer-reviewed. In Michigan, a cluster of more than 180 cases in June was traced to a restaurant and bar in East Lansing. And an indoor wedding in Maine in August is thought to have resulted in at least 176 coronavirus cases and seven deaths.
Those episodes and others suggest that although any infected person can spread the virus, there are circumstances in which transmissions can spiral out of control.
One major factor is the setting. The virus can be spread through airborne transmission, which means it can linger in tiny droplets in the air. That makes certain environments particularly risky, Lloyd-Smith said.
“A perfect storm is someone who is shedding a lot of virus in a space where they are able to share that virus effectively, so an indoor space without much ventilation with a lot of other people — and particularly if those people are inconsistent with practices like wearing masks,” he said.
But there’s also a lot of individual variation, and it’s not clear whether any infected person — given the right environmental factors — could become a superspreader.
“I don’t think we can differentiate whether it’s due to the individual or just the event,” said Seema Lakdawala, an assistant professor of microbiology and molecular genetics at the University of Pittsburgh School of Medicine. “I would argue that they are both really important.”
It’s thought that an infected person’s viral load — or the amount of virus that is actually in the body — plays an important role, but it’s unclear how.
“It’s nearly impossible to trace back to the actual individual-level traits in these superspreading events, because you don’t know they’re happening when they’re happening,” Lloyd-Smith said. “We can’t zip back in time and swab their nose for a sample at that critical moment of transmission.”
Another challenging aspect is that people infected with the virus can spread it before they experience any symptoms, which means some superspreaders could be exposing others without knowing they’re infected, Lakdawala said.
It’s also not known whether there are biological differences that make the virus more stable in certain people’s mucus, Lakdawala said. If that’s the case, it could mean superspreaders are just more effective at transmitting the pathogen when they cough, sneeze or speak….
While scientists are working to understand what factors are most important in creating superspreader events, there is mounting evidence that they are driving the bulk of the virus’s spread.” (F)
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- A.Coronavirus: What makes a gathering a ‘superspreader’ event?, By Holly Honderich,https://www.bbc.com/news/world-us-canada-53273382
- B.Was the Capitol riot a COVID-19 superspreader event?, by Chia-Yi Hou, https://thehill.com/changing-america/well-being/prevention-cures/533192-riots-at-the-capitol-could-be-a-coronavirus
- C.How the Trump-incited mob may have caused a COVID superspreader event, by BETH MOLE,https://arstechnica.com/science/2021/01/capitol-insurrection-was-recipe-for-covid-superspreader-event/
- D.A Riot Amid a Pandemic: Did the Virus, Too, Storm the Capitol?, by Apoorva Mandavilli, https://www.nytimes.com/2021/01/07/health/coronavirus-capitol-riot.html
- E.Could the Capitol Riot Become a Superspreader Event?, by Charlotte Klein, https://nymag.com/intelligencer/2021/01/could-the-capitol-riot-become-a-superspreader-event.html
- F.Covid-19 superspreader events emerge as focus of concern, By Denise Chow, https://www.nbcnews.com/science/science-news/covid-superspreader-events-emerge-focus-concern-n1242389