Antiviral susceptibility testing of pandemic (H1N1) 2009 influenza viruses (PDF, 91 KB) Information on viral susceptibility testing of pandemic (H1N1) 2009 influenza is provided in this document. Sequencing of virus from clinical samples can identify drug testing due to known mutations and virus isolates can be screened for resistance due to novel mutations by phenotypic methods. Added/updated: 21 December 2009