How far does a sneeze go?

Aren’t other people wonderful! Isn’t that person who bought the last punnet of strawberries (that you needed for your fruit salad tonight) just a delight. That stranger who sat next to you during a movie (when there were many free seats in the theatre) and ate pork crackling the entire time was just a treasure! And that man who let his dog poo on your newly mown lawn and left it there for you to discover is such a magical little pixie. Then there is your co-worker who obviously does not believe in holding anything in and gives full vent to a sneeze without restricting it with a tissue or even a crooked elbow. Perhaps you might deal with these wanton sneezers by retreating a few metres with some well placed, but surreptitious, dance steps. If this is your strategy then new research shows you might need to add a bit greater distance to your retreat if you really want to avoid droplets from the sneeze.

Previously research has suggested that larger mucus droplets from a sneeze or cough travel further than smaller droplets and that the distance travelled can be anywhere from two metres to six metres. If that news has you unsettled then the new research will send a chill down your spine.

Using high speed imaging of coughs and sneezes and using laboratory simulations and mathematical modelling to analyse the dynamics of these expulsions, these researchers have found that previous theories greatly underestimate the reach of a sneeze.

The researchers found that when mucus droplets merge with the gas cloud that accompanies a sneeze then their trajectory is altered compared to if they were travelling alone. A small droplet can be carried great distances by this cloud before it falls out. Everything changes when you analyse a sneeze from the point of view of the dynamics of a gas cloud rather than as individual droplets. So these researchers estimate that droplets around 100 micrometres in diameter could travel five times further than previously thought. Even more dramatically, droplets 10 micrometres in diameter could travel up to 200 times further than previously believed. These researchers say that any droplet less than 50 micrometres could travel far enough to enter air conditioning units.

That means of course, if you feel a sneeze coming on and you don’t have a tissue handy then in the interests of public health you will have to sacrifice the elbow crook of lovely cashmere sweater.