Published on March 21, 2016

A sneeze travels farther than you think

A sneeze travels farther than you think

From the most delicate, “achoo,” to a bombastic explosion of sound, the sneeze can break the silence in a room, or give away a movie villain hiding in the bushes.

We all do it, even marine and fresh water sponges. Like sponges, humans have cilia, tiny hair-like structures lining our nose and airway that help expel the irritants during a sneeze. This is how infection can spread from person to person. But just how far sneeze droplets can travel has been unknown until a recent study.

A team of researchers at the Fluid Dynamics of Disease Transmission Laboratory at the Massachusetts Institute of Technology decided to find out how a sneeze evolves and the distance droplets within it can travel. Reported in a paper entitled Visualization of sneeze ejecta: steps of fluid fragmentation leading to respiratory droplets by Lydia Bourouiba, the Esther and Harold E. Edgerton assistant professor, they videotaped two healthy individuals who sneezed about 50 times over several days.

The 3-D visualization techniques captured the sneeze droplets. The videos also showed that once the droplets hit the air, they have the potential to spew across a room and reach as high as ventilation ducts in a ceiling.

“When you are standing face to face with someone and they are sneezing, you know you are at risk for the droplets getting on you,” said Edward Caldwell, MD, an otolaryngologist at Cape Cod Hospital. “Now we know those droplets can travel 10 to 15 feet away from a person who is sneezing.”

Colds and flu viruses spread more easily than bacteria when sneezing because they are lighter and smaller, said Dr. Caldwell. But the most common transmission occurs when there is personal contact, such as shaking hands.

“In my office, I like to shake my patients’ hands, so I wash my hands before I enter the room and when I leave the room,” said Dr. Caldwell.

Studies have shown that we touch our face between 20 and 30 times a minute, so we are all transferring viruses and bacteria from our nose and mouth onto our hands, he said.

The Centers for Disease Control and Prevention recommends the following to prevent the spread of respiratory infections:

  • Cover your mouth and nose with a tissue when you cough or sneeze
  • Put your tissue in a waste basket
  • If you don’t have a tissue, cough or sneeze into your upper sleeve, not your hands
  • Wash your hands after coughing or sneezing, using soap and water
  • If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60% alcohol.

Dr. Caldwell also recommends getting the flu vaccine and urges people to stay home when they’re sick.

There are also a couple of steps we can take to keep our noses healthy. We get colds this time of year because our nasal passages are dry and under duress from the lack of humidity, said Dr. Caldwell. A humidifier and saline nasal spray keeps the nose moist and less susceptible to obstruction.