In the late 1800s, the German scientist Carl Flügge had a hunch: Maybe if you maintain enough physical distance between people who are sick and those who are well, you can prevent the spread of pathogens from person to person.
At the time, it was just a hypothesis, one that scientists like him often tried to test out using glass plates.
But it would take another four decades for technology to advance enough to confirm the idea, with the advent of high-speed photography.
In the early 1940s, scientists finally got their first glimpses of people's sneezes hurtling through the air in real time, at a capture rate of 30,000 frames a second, confirming that indeed, most of the stuff we throw into the air when we sneeze, cough, or yell tends to settle down to the ground within about a wingspan or so (say, 3 to 6 feet).
Here is one of those (revolting) first images:
|This photo of a sneezer caught in the act was taken by the professor Marshall Jennison from MIT and published in a 1941 research paper. Bettmann/Getty Images|
Back then, scientists maintained that most of the infectious gunk people expel (say, about 90% of their pathogens) travel less than 6 feet away.
Their study measurements were never meant to be taken as hard-and-fast rules about how far we should stand from other people during a pandemic, though.
Nevertheless, these 3-to-6-feet rules of thumb have become easy-to-follow protocols for keeping potentially sick people at arm's length during the coronavirus outbreak.
"The dogma was born," the professor Lidia Morawska, a leading aerosol scientist in Australia, said of the 80-year-old 6-foot rule. "Like any dogma, it's extremely difficult to change people's minds and change the dogmas."
But as the coronavirus pandemic drags on for months on end, Morawska and other leading air and virus scientists and engineers are starting to lead a charge toward dismantling the old 6-foot rule and taking a more nuanced approach to managing the novel coronavirus' spread.
Instead of always being on super-high alert, or assuming that a distance of 6 feet (or wearing masks, or washing hands) keeps us 100% safe all the time, they say, we should be learning how better to assess the situations we're in every day, letting our guard down now and again when it's relatively safe and moving back onto high alert when it's appropriate. Can we start thinking differently?
On Tuesday, hoping to inject a little more of such empowerment into the ways people protect themselves from the virus' spread, researchers from Oxford and MIT released a new traffic-light system that they hope will help people live life to its fullest while still being careful enough during the pandemic.
|This is the chart that Lydia Bourouiba and her co-authors designed to help people make better decisions about where it's safe to let your guard down, during the pandemic. The BMJ|
"We equip people with understanding to adapt in various situations so that they know when they need to be absolutely vigilant, and when they can let their guard down," she said.
The most important things to keep in mind when assessing the riskiness of any situation include taking a look at the environment you're in and acknowledging the density of the crowd and the activities people are doing.
|Café & Konditorei Rothe|
"There are three modes of transmission, and all three modes of transmission have to be controlled," she said.
Those three modes are people (the most common source of infection), surfaces, and the air.
"These things happen at the same time, and therefore distinguishing what's what is very difficult," Morawska said.
Life is more dangerous, then, in places where people become animated, excited, or otherwise loud in close confines, with stale air.
"Breathing out, singing, coughing, and sneezing generate warm, moist, high-momentum gas clouds of exhaled air containing respiratory droplets," Bourouiba and her coauthors wrote in the BMJ.
In such instances, a distance of even 20 to 30 feet may not be enough to protect you from an infection.
Meatpacking plants are then understandably ripe for viral spread because "the combination of high levels of worker contagion, poor ventilation, cramped working conditions, background noise (which leads to shouting), and low compliance with mask wearing" all contribute to viral spread, Bourouiba and her coauthors noted.
The same issue pops up easily in bars, gyms, indoor music venues, churches, and clubs.
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