The Flu Can Be Spread Just by Breathing, Study Suggests

As if we needed further confirmation that the flu is the worst, a new study suggests it’s not just coughing and sneezing that can spread the influenza virus—infected people may transmit it just by breathing. This finding comes as the government reports that flu is widespread in 49 states and 30 kids have died so far this flu season.

"We found that flu cases contaminated the air around them with infectious virus just by breathing, without coughing or sneezing," Donald Milton, professor of environmental health at the University of Maryland School of Public Health and lead researcher of the study, said in a statement. "People with flu generate infectious aerosols (tiny droplets that stay suspended in the air for a long time) even when they are not coughing, and especially during the first days of illness. So when someone is coming down with influenza, they should go home and not remain in the workplace and infect others." You literally have a doctor’s permission to go home if you’re getting the flu.

According to the study, there’s been little data about the amount and infectiousness of flu virus found in typical exhaled breath compared to coughing, sneezing, or touching infected surfaces—the ways we typically think the flu can spread. So researchers set out to shed light on that question by carefully studying exhalations from 142 people with confirmed cases of the flu.

They had people stick their faces in a machine aptly called the Gesundheit II for 30 minutes, captured samples from natural breathing, speaking, coughing, and sneezing and then examined the infectivity of the tiny droplets suspended in that exhaled air. Researchers had them visit this delightful setup on the first, second, and third day after flu symptoms began.

Their findings indicate that the flu can spread more easily than we thought, so yes, you really should stay home as soon as you start to feel the flu—please. Of 23 samples that didn’t involve coughing, 11 (48 percent) showed detectable viral RNA, the genetic material of the virus; and 8 of those 11 samples contained infectious virus. That means just breathing can theoretically spread the flu.

Interestingly, they found that sneezing didn’t produce greater numbers of viral RNA copies in the samples, which suggests it’s not an important contributor to virus shedding. That doesn’t mean you can just go around sneezing on people, either; it just means that sneezing doesn’t launch an especially large amount of viral material. The study was funded by the Centers for Disease Control and Prevention and the National Institutes of Health.

The results may also mean that our common-sense flu containment procedures aren’t enough. We may have to be even more vigilant. "The study findings suggest that keeping surfaces clean, washing our hands all the time, and avoiding people who are coughing does not provide complete protection from getting the flu," Sheryl Ehrman, study co-author and dean of the college of engineering at San José State University, said in a statement. "Staying home and out of public spaces could make a difference in the spread of the influenza virus."

The team says its findings could be use to develop better flu prevention measures on a public health level, like improving ventilation systems in offices, classrooms, and subway cars to reduce transmission risk. Until then, feel free to encourage your sick coworkers to stay home.

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