How far germs are expelled from the mouth when a person coughs is affected by various conditions, including the amount of saliva droplets expelled, the size of the droplets, and the airflow in the room or space, says LiveScience. Heavier droplets fall quickly; lighter ones are less affected by gravity.
When a person coughs, saliva droplets carrying germs are expelled from the mouth at speeds of up to 50 miles an hour, reports LiveScience. About 3,000 such droplets are expelled in a one cough. The lightest droplets, which are invisible to the naked eye, are largely unaffected by gravity and can float indefinitely, the distance they travel dictated by the space's airflow.