From BBC News
Also similar from same report at
https://www.straitstimes.com/singapore/health/coronavirus-keep-at-least-10m-away-if-running-behind-someone-to-avoid-infection-say and other places.
Presumably the cycling distance of 20m is for following, not passing sideways distance.
Runners should be 10m away, says research
Anna Holligan
BBC News reporter cycling in The Hague
With the gyms closed and public transport to be avoided, many of us are running or cycling or simply walking to keep fit, commute or just catch a breath of fresh air. But a group of scientists is warning we should perhaps beware.
While the standard social distancing rule between one to two metres may be effective when you are standing still inside, a new study says people who are in motion should be given a wider berth to avoid transmission of the coronavirus.
When a cyclist or pedestrian sneezes, coughs or even just exhales, the saliva particles are left behind in the air. Which means the person coming up behind them passes through this cloud of droplets.
By using methods used to enhance athletes' performances, the teams from Eindhoven University of Technology and Leuven University found the greatest risk of infection existed in the slipstream.
On the basis of these results, the scientists advise that those on the move should be given more of a social distance. Walkers should get at least four metres, runners 10 metres and cyclists at least 20 metres.
Jogging during the day has already been banned in Paris, and this study may encourage governments to revise the rules to ensure those who do go out are getting a healthy breath of fresh air - rather than one that might include a stranger's saliva particles.