The novel methodology and findings described here highlight the fate of infectious virus outside the respiratory tract as an important parameter for understanding influenza transmission. Direct measurements of airborne infectious virus and characterisation of their genotype and phenotype can significantly enhance the utility and quality of information obtained from ferret transmission studies.
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 of direct viral plaque isolation, researchers isolate and characterise infectious virus from droplets emitted by 2009 pandemic H1N1-infected ferrets, demonstrating 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.
Characterising viable virus from air exhaled by H1N1 influenza-infected ferrets reveals the importance of haemagglutinin stability for airborne infectivity. PLOS Pathogens. Published: February 25, 2020 https://doi.org/10.1371/journal.ppat.1008362
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