Coughing or sneezing is not always necessary to spread influenza. Breathing, alone, may result in airborne transmission of the virus, according to a study published in PNAS.
For the study, researchers enrolled 142 individuals with confirmed flu cases. Participants provided a total of 218 samples comprised of exhaled breath, spontaneous coughing and a few sneezes. Researchers obtained samples over three days after patients' onset of symptoms. Researchers also obtained 218 nasopharyngeal swab samples from patients.
Researchers identified viral RNA in 11 of the 23 fine aerosol samples acquired without coughing. Eight of these samples contained infectious influenza.
"We found that flu cases contaminated the air around them with infectious virus just by breathing, without coughing or sneezing," said Donald Milton, MD, the study's lead researcher and professor of environmental health at the University of Maryland School of Public Health in College Park. "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."
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