A research team at the Massachusetts Institute of Technology (MIT) has provided a very good reason for people to cover their mouths when coughing or sneezing.

According to the Boston Herald, the team found that coughs and sneezes leave a "cloud" of germ "droplets" that can spread throughout a room. Study co-author John Bush, an MIT professor of applied mathematics, said the new information could change the way ventilation systems are designed.

The range is huge," he told the Herald. "If you have a room and you're trying to decide how to ventilate the room, you have to keep in mind these pathogens stay in the air much longer."

The team published their work in the Journal of Fluid Mechanics.

Coughing or sneezing into a tissue eliminates this germ cloud, which people know exist, but cannot see or have not been able to prove.

"When you cough or sneeze, you see the droplets, or feel them if someone sneezes on you," Bush said in a press release. "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."

To study these clouds of germ particles, the team recorded coughs and sneezes using high-speed cameras. Until this study, many have assumed that the larger germ particles travel farther since their mass would give them more momentum.

The new study finds that when larger particles are clumped together, they do not travel as far, but they would if they stood alone. The smaller the particles are, the farther they can travel as a group. The researchers found this can increase a sneeze or cough's blast radius by anywhere from five to 200 times larger than previously thought.

The team's next objective is to analyze how different air conditions in various settings affect the longevity of a cough or sneeze's germ particle cloud.

"An important feature to characterize is the pathogen footprint," Bush said. "Where does the pathogen actually go? The answer has changed dramatically as a result of our revised physical picture."