COVID & Social Distancing: Is 6 Feet Enough?

August 27, 2020 – Just as we’ve gotten used to social distancing 6 feet from each other to slow the spread of COVID-19, scientists at the University of Oxford and the Massachusetts Institute of Technology suggest it does may not always be enough.

In a new study, researchers have found that the virus can travel on respiratory droplets up to 6 meters in just seconds after someone coughs, sneezes or sings.

The 6-foot guidance is based on an over-simplified scenario that examines how the virus is transferred by large or small airborne droplets without considering other factors. Transmission of the virus is more complex. It involves a range of droplet sizes and the activity that propelled the virus into the air. The research team evaluated published studies on the extent to which respiratory droplets of the coronavirus that causes COVID-19, as well as other viruses, can spread under different circumstances.

Based on these results, they suggest that a better model of social orientation at a distance is needed. Guidelines should take into account the setting, population density, length of time a person is present and whether people are wearing masks. Using this guide, a poorly ventilated and crowded environment where people are screaming and singing and not wearing face coverings would be at high risk. And an outdoor environment, well ventilated and less crowded, where people are calm and wear headgear, would be less risky.

Taking these factors into account when adjusting social distancing guidelines would mean more protection in high-risk settings, but also more freedom in low-risk settings – and perhaps a return to ‘normal’. , at least in certain situations.

Their result: The best social distancing depends on many factors that combine to determine the risk of transmitting the virus.

“It’s understandable to want to have a quick and easy rule of thumb for determining ‘how close is too close’, but biology is much more complicated than that,” says Kristin Bratton Nelson, PhD, assistant professor of epidemiology at the School. Rollins Public Health Department at Emory University in Atlanta. She researched the super-diffusion of COVID-19 in Georgia.

She agrees with the researchers that recommendations should reflect this nuance and provide clear guidance on the riskiest activities.

“I’ve seen in recent weeks that there are still policies in place to shut down outdoor spaces, like parks, beaches and playgrounds, in the name of reducing transmission. I think it’s really misguided, and maybe even counterproductive, if they push interactions in. “

Len Horovitz, MD, pulmonologist at Lenox Hill Hospital in New York City, says you need to think of the risk of COVID transmission more like smoking. “When you breathe out cigarette smoke, you can see that it is over 6 feet.”

The risk of transmitting COVID-19 depends a lot on the circumstances, says Horovitz, who was not involved in the study. “The interior is much riskier than the exterior.” Particle size matters, he says. “If he’s smaller, he can travel faster.” The risk, he says, “depends on your activity, the movement of air in the room, the humidity and how long you stay in the room.” Viral load – or the level of virus in a person’s airways – also varies from person to person, he says.

He encourages people to consider all of these things when deciding the degree of social distancing. “If you wear a mask, don’t scream, aren’t sick, keep your mask on, and there’s ventilation inside, 6 feet is probably enough.”

Bratton Nelson agrees that there is a range of transmission risks.

It is important to keep this in mind not only when considering how far away from others physically you must be, but also when considering which activities are safe.

“There is no ‘safe’ and ‘not sure’,” she says, but by determining which activities and environments are the safest, people can try to focus on those.

Sources

The BMJ: “Two meters or one: what is the evidence for physical distance in covid-19?”

BMJ press release: “Rigid social distancing rules for covid-19 based on outdated science.”

Len Horovitz, MD, pulmonologist, Lenox Hill Hospital, New York.

Kristin Bratton Nelson, PhD, Assistant Professor of Epidemiology, Emory University Rollins School of Public Health, Atlanta.


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