A Sneeze May Be Even Ickier Than You Thought
Slow-motion photos reveal a 'sheet' of expelled fluid that then breaks apart, researchers say
By Robert Preidt
FRIDAY, Feb. 12, 2016 (HealthDay News) -- If you think your sneezes merely emit a delicate spray of tiny droplets into the space around you, think again.
New research from the Massachusetts Institute of Technology using slow-motion photography finds that, instead, sneezes expel a sticky sheet of fluid that first balloons and then breaks apart into long, viscous filaments.
Those filaments eventually do separate into a mist of fine droplets, said a team led by Lydia Bourouiba, who runs MIT's Fluid Dynamics of Disease Transmission Laboratory.
"What we saw was surprising in many ways," she said in a university news release. "We expected to see droplets coming out fully formed from the respiratory tract. It turns out that's not the case at all."
All of this research could lead to more effective ways to reduce the spread of illness, her team said.
"It's important to understand how the process of fluid breakup, or fluid fragmentation, happens," Bourouiba explained. Knowing how sneezing disperses droplets can help scientists map the spread of infections and identify people who may be "super-spreaders," she said.
In prior research reported in 2014, her team found that coughs and sneezes emit "clouds" of gas that spread infectious droplets more than 200 times farther than would happen if they were just separate drops.
In the new study, Bourouiba's team used high-speed cameras to record more than 100 sneezes from volunteers, who had their noses tickled to produce the sneeze. The photos -- comprising a time span of under 200 milliseconds -- were able to capture the precise moment when saliva is expelled from the mouth and launched into the air.
Sneezes also varied from person to person, the study found, because some people have more elastic saliva than others. For sneezers with the stickier saliva, expelled fluid tended to keep its stringy, filament shape longer, forming beads that in time became droplets.
All of this is important to help scientists "understand how the process of fluid breakup, or fluid fragmentation, happens," Bourouiba said, and "the resulting prediction of the downstream range of contamination."