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A controversial simulation has been widely shared online, suggesting that people exercising outdoors should keep between 13 and 65 feet from others to prevent the spread of coronavirus-infected droplets.
The CDC recommends people keep 6 feet of distance between themselves and others in public spaces.
There are plenty of issues with the simulation. One epidemiologist told Vice, "It makes my blood boil"
An infectious-disease expert told Business Insider that staying farther than 6 feet from others is smart, but people should not be panicking about joggers 32 feet from them.
A widely shared animation made by a team of engineers has stoked controversy among infectious-disease experts and confusion among the public about how the coronavirus is spread outdoors.
The simulation, which was done by researchers at KU Leuven, in Belgium, and TU Eindhoven, in the Netherlands, shows two people running with a cloud of colorful particles floating in their wake.
The researchers, who shared the video with local newspaper Het Laatste Nieuws — but have yet to write it up into a study — said their findings suggest people walking outdoors should stay at least 13 feet from others walking in the same direction, runners and slower cyclists should stay at least 32 feet from others, and cyclists riding rigorously should stay 65 feet away.
The findings were shared widely on social media after they was described in a Medium blog post written by Juergen Tholen, an entrepreneur.
In his post, Tholen describes the animation as a "study" that "I will be taking into account," adding that he will now be running in streets instead of busy parks.
But as Vice's Jason Koebler said, it is not a study — the only write-up the research team has published is a direct translation of the Het Laatst Nieuws article, which contains very little explanation of how the simulation was made.
The problems with the simulation are plenty. The researchers are engineers, not infectious-disease or virology experts, and they have not had their work reviewed by their peers, a crucial step in scientific research, particularly when it comes to studies that could influence how people act and treat each other and affect their mental health during the pandemic.
The simulation — and the hype over it — is dangerous, according to infectious-disease experts
The biggest problem is that Blocken's team did not write up their methodology. Blocken told Vice he went to the media before writing up a study because of the pandemic, saying the public deserved to hear his findings before going through the notoriously slow process research usually requires to get published.
His critics say he could have followed the example of most other researchers studying the coronavirus by posting a pre-print on biorxiv.org or medrxiv.org, sites where scientists can upload their work to be quickly and publicly reviewed by their peers.
The second fundamental issue with the simulation is that Blocken's team does not address how the coronavirus travels in the air.
Blocken's team has released few details about how they predicted the size of human-saliva particles that joggers, cyclists, and walkers give off. Speaking to Het Laatste Nieuws, lead researcher Bert Blocken, a professor of civil engineering, said they used models including wind force to calculate how much distance passersby should keep when they see somebody exercising.
But the consensus among virologists — researchers who specifically study how viruses act, move, and transmit — is that there is no consensus on how the novel coronavirus travels in the air.
We do know that the coronavirus typically travels in droplets — heavier particles that can be coughed or sprayed up to 6 feet from someone's mouth, or linger on surfaces that they drop on, as Business Insider's Aylin Woodward has reported. The key is to avoid touching communal surfaces while staying at least 6 feet from others.
That's unlike other viruses, such as measles, which travel in aerosols — minuscule particles that can drift through the air and linger for hours.
But it's not clear-cut: One not-yet-peer-reviewed study found traces of coronavirus particles in the air at the other end of a corridor from the original source, though it's unclear whether those particles were infectious. Another study in Italy found the virus may spread more freely in highly polluted areas.
There is also evidence the virus could be sprayed farther than 6 feet by singing and loud talking. Again, it's unclear if the particles would be infectious at the end of their journey.
"It gets very nuanced," William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University, told Business Insider.
William Hanage, an epidemiologist at Harvard's Center for Communicable Disease Dynamics, told Vice the attention and confusion over Blocken's simulation is "concerning," the research is "not really useful," and, overall, it "makes my blood boil."
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It's a good idea to stay more than 6 feet from others, but you don't have to be paranoid when you go for a walk
While the simulation, and the way it has been shared, has flaws, Schaffner says there's no harm in trying to keep more than 6 feet from others, as the CDC recommends, given that there is evidence that droplets can travel farther.
"The larger particles often are broadcast, spread more widely, because you're exhaling them with more energy," Schaffner said. "No, you don't have to carry a yard stick with you or, you know, a collapsible tape measure, or something like that. I mean, just keep a sensible distance from people."
According to Schaffner, there could be merit to Blocken's model, but it's only really important for people who are in enclosed spaces or in very crowded areas.
People should not panic about joggers 32 feet from them and should not be afraid to go outside for a walk. As The Atlantic's Ed Yong reported, even the most cautious virologists say the mental-health benefits of a stroll in the park outweigh any risks.
Schaffner said that everyone should wear a mask and be careful about keeping their distance if they're going to the pharmacy or the grocery store. But it's fine to be mask-free in an open sparsely populated park.
"If you're out walking by yourself and there's nobody in the park, no, you don't have to wear the mask," Schaffner said. "A modicum of good judgment, rather than a list of 73 rules, I think that will get us 99% of the way."
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