Virologists and epidemiologists told NPR back in late May that using a public restroom was, perhaps surprisingly, "low to medium risk" during the coronavirus pandemic, with a few caveats (gas station bathrooms, for example). "There are all sorts of things that you can catch from other people's poop, and you almost never do, because they're set up with all hard surfaces that can be cleaned," said Dr. Emily Landon, an infectious diseases specialist at University of Chicago Medicine. A study published Tuesday in the journal Physics of Fluids found that "other people's poop" can almost certainly spread COVID-19, in an appropriately disgusting manner.
"Scientists have found that in addition to clearing out whatever business you've left behind, flushing a toilet can generate a cloud of aerosol droplets that rises nearly three feet," The New York Times reports. "Those droplets may linger in the air long enough to be inhaled by a shared toilet's next user, or land on surfaces in the bathroom," potentially spreading "infectious coronavirus particles that are already present in the surrounding air or recently shed in a person's stool."
Researchers already knew that feces can contain viable coronavirus particles — some cities have successfully tested sewage to detect the prevalence of COVID-19 in an area — and previous coronaviruses like SARS spread through infectious fecal aerosols. It isn't clear yet how much a risk that is with this new coronavirus. But the new findings are "very alarming," said Yangzhou University fluid dynamics researcher Ji-Xiang Wang, co-author of the study. There is a pretty simple workaround, though, he told the Times: "Close the lid first and then trigger the flushing process."
Other people looking at this issue have come up with other solutions, like ultraviolet lights or automated disinfectant spray, the Times notes, but University of Nebraska microbiologist Joshua Santarpia suggested making lemonade out of this aerosolized fecal stew. "You could simply monitor samples from a shared bathroom on a daily basis," he said. "And if something were to come up positive, you could then go look at everyone who was there and who they had contact with, rather than testing everybody all the time."