The transmissibility and pandemic potential of influenza viruses depends on their ability to efficiently replicate and be released from an infected host, retain viability as they pass through the environment, and then initiate infection in the next host. There is a significant gap in knowledge about viral properties that enable survival of influenza viruses between hosts, due to a lack of experimental methods to reliably isolate viable virus from the air. Using a novel technique, we isolate and characterise infectious virus from droplets emitted by 2009 pandemic H1N1-infected ferrets. We demonstrate that infectious virus is predominantly released early after infection. A virus containing a mutation destabilising the haemagglutinin (HA) surface protein displayed reduced survival in air. Infectious virus recovered from droplets exhaled by ferrets inoculated with this virus contained mutations that conferred restabilisation of HA, indicating the importance of influenza HA stability for between-host survival. Using this unique approach can improve knowledge about the determinants and mechanisms of influenza transmissibility and ultimately could be applied to studies of airborne virus exhaled from infected people.
Bibliographical noteFunding Information: This work was funded by Wellcome Trust grants WT105736MA (A.S) and 200187/Z/15/Z (J.Z and R.F) (Wellcome Trust - https://wellcome.ac.uk/), NC3Rs grants G1000033/1 and NC/K00042X/1 (R.A.E) (National Centre for the Replacement, Refinement & Reduction of Animals in Research (NC3Rs) - https://www.nc3rs.org.uk/), and L.N. was supported by the Johns Hopkins Provosts Visiting Scholarship (Johns Hopkins University - http://facultyaffairs.jhu.edu/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Open Access: . This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Publication copyright: © 2020 Singanayagam et al.
Citation: Singanayagam A, Zhou J, Elderfield RA, Frise R, Ashcroft J, Galiano M, et al. (2020) Characterising viable virus from air exhaled by H1N1 influenza-infected ferrets reveals the importance of haemagglutinin stability for airborne infectivity. PLoS Pathog 16(2): e1008362.