Laboratory methodologies for testing the antiviral susceptibility of influenza viruses
The need for surveillance of antiviral susceptibility of influenza viruses has grown in recent years. The laboratory methodologies described below have been developed and reviewed by an Expert Working Group on Antiviral Susceptibility for the WHO Global Influenza Surveillance and Response System (GISRS). They are intended for National Influenza Centres in GISRS and other laboratories that test for influenza antiviral susceptibility.
M2 ion channel inhibitor
Approaches to M2 inhibitor resistance testing
M2 inhibitor resistance is associated with amino acid substitutions, due to single-nucleotide polymorphism (SNP) between residues 26-34 in the transmembrane domain of the M2 protein. The most commonly detected M2 amino acid substitution that confers M2 inhibitor resistance is S31N.
The frequency of M2 inhibitor resistance in currently circulating seasonal influenza A viruses is very high (>99%) . The M2 inhibitors are also ineffective against influenza B viruses. Consequently, WHO does not recommend the use of the M2 inhibitors for the treatment of patients infected with circulating seasonal influenza viruses.
M2 inhibitor resistance testing is thus not considered a priority activity for National Influenza Centres in GISRS.
Neuraminidase inhibitor (NAI)
Polymerase acidic (PA) protein inhibitor
Monitoring antiviral resistance in influenza viruses with pandemic potential using Tool for Influenza Pandemic Risk Assessment (TIPRA)
Global updates on the susceptibility of human or animal influenza viruses to antivirals
Meetings of the WHO working group on surveillance of influenza antiviral susceptibility
13th Meeting, short summary report, June 2024, Lyon, France
Reports published in the Weekly Epidemiological Record
12th Meeting, June 2023, Rio de Janeiro, Brazil
11th Meeting, June 2022, Istanbul, Türkiye
10th Meeting, November 2021, Geneva, Switzerland (virtual meeting)
9th Meeting, October 2020, Geneva, Switzerland (virtual meeting)
7th Meeting, August 2018, Saint Petersburg, Russian Federation
6th Meeting, April 2017, Hong Kong, China Hong Kong Special Administrative Region
4th Meeting, May 2014, Geneva, Switzerland
3rd Meeting, July 2013, Geneva, Switzerland
1st and 2nd Meeting, November 2011 and June 2012, Geneva, Switzerland
Publication
Practical guidance for national influenza centres establishing or implementing neuraminidase inhibitor...
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