It doesn’t take a germophobe or hypochondriac to know that someone sneezing near you – without covering his or her nose and mouth – can be an unpleasant experience.
How safe are you from the germs that the person sitting opposite you on the MRT has just unleashed again and again? Do you actually need to move to the next cabin?
First, the facts. Yes, experts have actually tracked the distance that droplets produced through sneezing can travel. According to a 2014 study by the Massachusetts Institute of Technology (MIT), they can fly quite far and come in two phases: Droplets and gas clouds.
“When you cough or sneeze, you see the droplets, or feel them if someone sneezes on you,” said Professor John Bush, a MIT professor of applied mathematics and co-author of a paper published in the Journal Of Fluid Mechanics.
“But you don’t see the cloud, the invisible gas phase.” Cue: Ominous music.
HOW FAR CAN SOMEONE'S SNEEZE DROPLETS REACH?
According to the paper's other co-author, Lydia Bourouiba, an assistant professor at MIT’s Department of Civil and Environmental Engineering, the largest droplets quickly settle within 1m to 2m away from the guilty party.
But there’s more: The "smaller and evaporating droplets are trapped in a turbulent puff cloud,” said Dr Bourouiba. And over the course of seconds to a few minutes, these "can travel the dimensions of a room and land up to 6m to 8m away.”
DOES THAT MEAN THERE'S NO ESCAPING SOMEONE'S GERMS?
Actually, there is – and strangely enough, it’s thanks to our weather.
Separate studies similar to MIT's have also been done in Singapore and Hong Kong from 2010 to 2012. Both tests, published in the scientific journal PLOS One in 2014, set out to test how transmissible the influenza virus is by real-life infected subjects.
Both studies had infected participants breathe, talk and cough at mannequins from various distances from 10cm to 1m before swabbing their surfaces for viruses.
Interestingly, both studies independently found that "influenza may not be particularly transmissible by the aerosol route in most circumstances", even when large droplets were detected and tested.
The largest droplets rapidly settle within 1m to 2m away from the guilty party. But the smaller and evaporating droplets are trapped in a turbulent puff cloud.
Dr Jyoti Somani, senior consultant from National University Hospital's Division of Infectious Diseases, theorised that Singapore's high humidity might have kept the viral particles wet and thus, heavier, so they would not be able to spread as far as in the MIT study.
I’D STILL RATHER NOT BREATHE IN. CAN I ESCAPE THESE DROPLETS IF I HOLD MY BREATH AND MOVE AWAY?
It depends. If someone with the flu unexpectedly sneezes within 2m of where you are, you’re likely to have already breathed in the droplets, said Dr Edwin Chng, medical director of Parkway Shenton.
It might work better holding your breath if you anticipate a sneeze from someone close by and move away before he or she sneezes. “If you do not move away fast enough, some droplets may land in the mouth or nose, and can still result in an infection,” he said.
Dr Somani added that it’s still helpful to move away from a sneezer after the deed. "This is because the surrounding air and surfaces of things nearby, including the person's clothes, seat and railings can get contaminated with viral germs that you might touch by accident."
But you needn't panic, said Professor Paul Tambyah from the NUS Yong Loo Lin School of Medicine's Department of Medicine as well as Centre for Biomedical Ethics
As the Hong Kong and Singapore studies showed, "few of those particles we inhale or ingest actually end up causing disease", he said.
"Also, the body has plenty of mechanisms to prevent infection such as the normal host immune response or our instinctive response to wipe away someone else’s snot if they sneeze on us. That is the normal response in most societies with good reason!"
MY CHILD HAS THE FLU AND JUST SNEEZED INTO MY FACE. WILL I FALL SICK, TOO?
The good news: Most parents are already immune to many of the strains of viruses that their children may be carrying, said Prof Tambyah. "Most adults are immune to the common childhood viruses circulating in the country, especially if they grew up here."
Dr Chng agreed: “Not everyone who is exposed to the virus will fall sick as some individuals' immune system can resist it". If you're bothered, “washing or wiping the faces immediately helps to remove any droplets that land in the mouth or nose of the parent, hence reducing the chances of falling ill."
IF I’M THE ONE SNEEZING, IS COVERING THE NOSE AND MOUTH REALLY THE BEST WAY TO DO SO?
“The best way to minimise the spreading of droplets is to cover your mouth and nose with a tissue and throwing it away immediately,” said Dr Chng.
But if you don't have tissue on you, “it is better to sneeze into the crook of your elbow because when you use your hands to cover your nose, they get contaminated with the droplets,” he said. “This, in turn, will contaminate objects or people that you touch afterwards.” If you can't help it and sneeze into your hand, he recommended washing your hands immediately.