The 6 feet of separation touted by the CDC might not be enough to prevent the spread of the coronavirus, particularly among runners. A new study described in the New York Times suggests air carries respiratory droplets up to 30 feet behind runners and up to 15 feet behind fast walkers, meaning anyone in that vicinity could become infected. There's reason to be cautious because the study, based on computer models, hasn't been published in a peer-reviewed journal and didn't look at coronavirus particles specifically. "Still, its calculations make sense," per the Times. The study found large respiratory droplets were pulled into the long, narrow slipstream behind a runner or walker—about the width of the person's shoulders.
A team from Oklahoma State University similarly found that a person running a 10-minute-mile pace behind another runner would be exposed to droplets even with 6 feet of distance maintained, per WFXT. The team concluded that even a light breeze could carry droplets farther than 6 feet, suggesting such a distance is only suitable for social distancing in static ambient air. A third study out of Western University, looking at how influenza is passed through coughs, found droplets traveled 6 feet in three seconds before continuing "well beyond the recommended six feet," per the National Post. Droplets might even travel up to 27 feet, per Quartz, which notes the CDC's social distancing guideline "may be outdated." (We could be in this for the long haul.)