Airborne Transmission of Influenza A/H5N1 Virus Between Ferrets

Sander Herfst et al. Science 336, 1534 (2012)

Speaker：Chan- Yi Su (蘇展儀)                )                                  Time：13:10~14:00 Feb. 20, 2013

Commentator：Ai-Li Shiau, Ph.D. (蕭璦莉老師)  )  Place: Room 601

Abstract

Highly pathogenic avian H5N1 influenza A virus remains a pandemic threat, but currently does not transmit efficiently among humans. Whether this virus may acquire the ability to be transmitted via aerosol or respiratory droplet (“airborn transmission”) among mammals, including humans, to trigger a future pandemic is a key concern for pandemic preparedness. To address this question, the authors first inserted several known mutations which might help the virus adapt for mammalian spread, but didn’t make the virus transmissible. Next, the authors serially passed the mutant virus in ferrets to encourage a pathogen to adapt to a new host. After 10 rounds of passages, the virus acquired additional mutations which were consistently passed from one ferret to the next in 3 of 4 cases. The result suggested that airborn transmission requires as few as five amino acid substitutions (four in HA and one in PB2). None of the recipient ferrets died after airborn infection with the mutant A/H5N1. The airborne-transmission viruses were sensitive to the antiviral drug oseltamivir and reacted well with antisera raised against H5 influenza vaccine strains. In sum, this study indicates that A/H5N1 viruses have the potential to evolve directly to transmit by airborn transmission, without reassortment in any intermediate host, and thus pose a risk of becoming pandemic in humans.

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