Sneezes and coughs can cause germs to travel much farther than previously believed, according to a new study by researchers from the Massachusetts Institute of Technology.
Mist is often seen coming from the mouth of a person as they sneeze, but this is not the only way germs travel. A larger, invisible gas could also contains viruses that can spread the disease.
"When you cough or sneeze, you see the droplets, or feel them if someone sneezes on you. 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," John Bush of MIT, co-author of the journal article announcing the results.
High-speed film was used to record people as they sneezed and coughed. Observations were combined with mathematical modeling and computer simulations to investigate the nature of infection.
Researchers found viruses are able to travel five to 200 times farther than believed while accompanied by these clouds of turbulent air. New ideas about how viruses spread were developed by the research. It was believed that larger viruses would travel farther than smaller organisms, since they have a higher momentum. Investigators found the velocity of the tiny organisms is greatly affected by interactions with other viruses regardless of size, overturning this earlier notion.
"Violent respiratory events such as coughs and sneezes play a key role in transferring respiratory diseases between infectious and susceptible individuals," researchers wrote in the article detailing their finding.
Results of the study show viruses 0.004 inches across travel five times further than previously believed, while those one-tenth that size can fly 200 times farther than early models predicted. Viruses measuring 0.002 inches across or smaller were found to remain in the air long enough that they could reach ventilation systems, and be distributed around an office or apartment building.
Ventilation systems may be more apt to carry germs than previous theories estimated. This new finding could affect the way air circulation systems are designed and managed. Filters for air systems may need to be redesigned and reclassified after this new research.
"You can have ventilation contamination in a much more direct way than we would have expected originally," Lydia Bourouiba, assistant professor at MIT and co-author of the study, stated in a press release announcing the finding.
Study of how viruses travel in the air was detailed in the Journal of Fluid Mechanics.
