Little is known about the amount and infectiousness of influenza virus shed into exhaled breath. This contributes to uncertainty about the importance of airborne influenza transmission.
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Finding infectious virus in 39% of fine-aerosol samples collected during 30 min of normal tidal breathing in a large community-based study of confirmed influenza infection clearly establishes that a significant fraction of influenza cases routinely shed infectious virus, not merely detectable RNA, into aerosol particles small enough to remain suspended in air and present a risk for airborne transmission.
Full Paper: pnas.org/content/early/2018...
Popularisation: newatlas.com/flu-spread-bre...
Note: A 2013 study from the same team found that wearing a surgical mask significantly reduces the transmission of influenza via airborne droplets. So it doesn't really matter if you aren't coughing or sneezing, you still are effectively transmitting the flu to others just by breathing near them unless you wear a mask.
Not at all comforting news if you are out and about...
Neil