tetano
Editor, Senior Moderator
Influenza Other Respir Viruses
. 2026 Sep;20(9):e70312.
doi: 10.1111/irv.70312.
Saira Hussain 1 2 , Charmaine Chia 3 , Ashwin Muraleetharan 1 , Yi-Mo Deng 1 , Xiaomin Dong 1 , Presa Chanthalavanh 1 , Emi Takashita 4 , Clyde Dapat 1 , Jessica E Miller 1 5 , Heidi Peck 1 , Raphael T C Lee 3 , Jan Williamson 6 , Louise Cooley 7 , Sebastian Maurer-Stroh 3 8 9 , Ian G Barr 1 2
Affiliations
The emergence of viruses with reduced susceptibility to antivirals poses an ongoing risk which could limit their effectiveness. Here we report a cluster of A(H3N2) viruses detected in Tasmania, Australia, with a PA gene mutation A37T that showed mild reductions in susceptibility in vitro to baloxavir (3.47- to 16.33-fold increased EC50) when compared to wild-type influenza A(H3N2) viruses. When the PA-A37T and PA-I38T substitutions were combined and tested in IRINA assay, eightfold higher inhibition was seen compared to PA-I38T alone. On-going monitoring of influenza viruses for reduced susceptibility to antivirals remains an important part of seasonal and zoonotic influenza surveillance.
Keywords: antiviral susceptibility; baloxavir; influenza A viruses
. 2026 Sep;20(9):e70312.
doi: 10.1111/irv.70312.
A Cluster of Influenza A(H3N2) Viruses in 2024 From Tasmania, Australia, With Reduced Susceptibility to Baloxavir
Saira Hussain 1 2 , Charmaine Chia 3 , Ashwin Muraleetharan 1 , Yi-Mo Deng 1 , Xiaomin Dong 1 , Presa Chanthalavanh 1 , Emi Takashita 4 , Clyde Dapat 1 , Jessica E Miller 1 5 , Heidi Peck 1 , Raphael T C Lee 3 , Jan Williamson 6 , Louise Cooley 7 , Sebastian Maurer-Stroh 3 8 9 , Ian G Barr 1 2
Affiliations
- PMID: 42778508
- PMCID: PMC13601022
- DOI: 10.1111/irv.70312
Abstract
The emergence of viruses with reduced susceptibility to antivirals poses an ongoing risk which could limit their effectiveness. Here we report a cluster of A(H3N2) viruses detected in Tasmania, Australia, with a PA gene mutation A37T that showed mild reductions in susceptibility in vitro to baloxavir (3.47- to 16.33-fold increased EC50) when compared to wild-type influenza A(H3N2) viruses. When the PA-A37T and PA-I38T substitutions were combined and tested in IRINA assay, eightfold higher inhibition was seen compared to PA-I38T alone. On-going monitoring of influenza viruses for reduced susceptibility to antivirals remains an important part of seasonal and zoonotic influenza surveillance.
Keywords: antiviral susceptibility; baloxavir; influenza A viruses