Flu Even Spreads Through Breathing
The influenza virus can not only be spread through sneezing and coughing, but also simply through exhaled air, a new study found.1
For their study, the researchers assessed 355 symptomatic participants with acute respiratory illness and 142 cases with confirmed influenza. They collected a total of 218 paired nasopharyngeal (NP) and 30-minute breath samples (coarse: more than 5-µm fractions; fine: 5-µm fractions or less) from participants during the first 3 days following symptom onset, and assessed viral RNA copy numbers for all samples, cultured NP swabs, and fine aerosols.
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Findings showed that influenza virus had been recovered from 52 (39%) of the fine aerosols and 150 (89%) of the NP swabs with valid cultures, with geometric mean RNA copy numbers of 3.8 × 104/30-minutes fine-, 1.2 × 104/30-minutes coarse-aerosol sample, and 8.2 × 108 per NP swab.
Notably, the researchers found that coughing and sneezing were not necessary for infectious aerosol generation. They found positive associations of fine- and coarse-aerosol viral RNA with body mass index and number of coughs, and negative associations of fine- and coarse-aerosol viral RNA with increasing days since the onset of symptoms.
“We found that flu cases contaminated the air around them with infectious virus just by breathing, without coughing or sneezing,” said Dr. Donald Milton, MD, MPH, professor of environmental health in the University of Maryland School of Public Health. “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.”2
—Christina Vogt
Reference:
1. Yan J, Grantham M, Pantelic J, et al. Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community [Published online January 18, 2018]. PNAS. doi:10.1073/pnas.1716561115.
2. Flu may be spread just by breathing, new study shows; coughing and sneezing not required [press release]. University of Maryland. January 18, 2018. https://sph.umd.edu/news-item/flu-may-be-spread-just-breathing-new-study-shows-coughing-and-sneezing-not-required.