How cough, sneeze float farther than you think

A study shows that coughs and sneezes have associated gas clouds that keep their potentially infectious droplets aloft over much greater distances than previously realized.

“When you cough or sneeze, you see the droplets, or feel them if someone sneezes on you,” says John Bush, a professor of applied mathematics at MIT, and co-author of a new paper on the subject.

“But you don’t see the cloud, the invisible gas phase. The influence of this gas cloud is to extend the range of the individual droplets, particularly the small ones,” Medical Web Times wrote.

Indeed, the study finds the smaller droplets that emerge in a cough or sneeze may travel five to 200 times further than they would if those droplets simply moved as groups of unconnected particles, which is what previous estimates had assumed.

The tendency of these droplets to stay airborne, re-suspended by gas clouds, means that ventilation systems may be more prone to transmitting potentially infectious particles than had been suspected.

With this in mind, architects and engineers may want to reexamine the design of workplaces and hospitals, or air circulation on airplanes, to reduce the chances of airborne pathogens being transmitted among people.

“You can have ventilation contamination in a much more direct way than we would have expected originally,” says Lydia Bourouiba, an assistant professor in MIT’s Department of Civil and Environmental Engineering, and another co-author of the study.

The researchers used high-speed imaging of coughs and sneezes, as well as laboratory simulations and mathematical modeling, to produce a new analysis of coughs and sneezes from a fluid-mechanics perspective. Their conclusions upend some prior thinking on the subject.

Source: Iran Daily
Published: 10 Apr 2014

Category: Features