Zhou, JieWei, JianjianChoy, Ka-TimSia, Sin FunRowlands, Dewi K.Yu, DanWu, Chung-YiLindsley, William G.Cowling, Benjamin J.McDevitt, JamesPeiris, MalikLi, YuguoYen, Hui-Ling2018-05-302018Zhou, J., J. Wei, K. Choy, S. F. Sia, D. K. Rowlands, D. Yu, C. Wu, et al. 2018. “Defining the sizes of airborne particles that mediate influenza transmission in ferrets.” Proceedings of the National Academy of Sciences of the United States of America 115 (10): E2386-E2392. doi:10.1073/pnas.1716771115. http://dx.doi.org/10.1073/pnas.1716771115.http://nrs.harvard.edu/urn-3:HUL.InstRepos:37068229Epidemics and pandemics of influenza are characterized by rapid global spread mediated by non-mutually exclusive transmission modes. The relative significance between contact, droplet, and airborne transmission is yet to be defined, a knowledge gap for implementing evidence-based infection control measures. We devised a transmission chamber that separates virus-laden particles by size and determined the particle sizes mediating transmission of influenza among ferrets through the air. Ferret-to-ferret transmission was mediated by airborne particles larger than 1.5 µm, consistent with the quantity and size of virus-laden particles released by the donors. Onward transmission by donors was most efficient before fever onset and may continue for 5 days after inoculation. Multiple virus gene segments enhanced the transmissibility of a swine influenza virus among ferrets by increasing the release of virus-laden particles into the air. We provide direct experimental evidence of influenza transmission via droplets and fine droplet nuclei, albeit at different efficiency.en-USMicrobiologyinfluenza virusdroplet transmissionairborne transmissionairborne particlesferretsJournal Article2018-05-3010.1073/pnas.1716771115