If someone exhales, coughs or sneezes while walking, running or cycling, most of the microdroplets are entrained in the wake or slipstream behind the runner or cyclist. The other person who runs or cycles just behind this leading person in the slipstream then moves through that cloud of droplets.

The slipstream is the zone that arises right behind a person when they are walking or cycling, and which pulls the air a bit along with this moving person, as it were.

Cyclists like to position themselves in the slipstream of others to reduce their air resistance. But someone who walks or runs also has such a slipstream. We have seen that no matter how that zone forms, droplets end up in that air stream. So it’s best to avoid that slipstream.