10th Meeting of the WHO Expert Working Group of the Global Influenza Surveillance and Response System for Surveillance of Antiviral Susceptibility/Dixieme reunion du groupe de travail d'experts de l'OMS sur la surveillance de la sensibilite aux antiviraux dans le cadre du Systeme mondial de surveillance de la grippe et de riposte.

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Date: Apr. 1, 2022
From: Weekly Epidemiological Record(Vol. 97, Issue 13)
Publisher: World Health Organization
Document Type: Article
Length: 2,229 words
Lexile Measure: 1960L

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Executive summary

The WHO Expert Working Group on Surveillance of Influenza Antiviral Susceptibility (AVWG) supports the WHO Global Influenza Surveillance and Response System (GISRS) by providing practical guidance for monitoring the susceptibility of seasonal and emerging influenza viruses to antivirals through global surveillance. The 10th AVWG meeting was held virtually on 2-4 November and 6 December 2021.

Update on susceptibility of seasonal and zoonotic influenza viruses to approved antiviral agents

Global human seasonal influenza activity has remained low since declaration of the COVID-19 pandemic in March 2020. In 2020-2021, WHO collaborating centres reported low activity of A(H1N1)pdm09, A(H3N2) and B/Victoria seasonal influenza viruses and a low detection frequency of variants with reduced susceptibility to approved antiviral agents. No variant with neuraminidase (NA) amino acid substitution that reduces susceptibility to NA inhibitors (NAIs) was detected between September 2020 and May 2021. An amino acid substitution in the polymerase acidic (PA) protein E23K, associated with reduced susceptibility to baloxavir marboxil (baloxavir), was detected in a single A(H1N1)pdm09 isolate from Togo. Increasing numbers of zoonotic and avian influenza viruses have been monitored for antiviral susceptibility in sequence-based analysis or phenotypic assays. None of the analysed zoonotic or avian influenza viruses had PA or NA amino acid changes known to confer reduced susceptibility to baloxavir or NAIs or showed reduced susceptibility to baloxavir or NAI in phenotypic assays.

Update of protocols and guidance for GISRS laboratories

The guidance on assay protocols and interpretation of influenza susceptibility to NAIs was last updated in 2018. (1) Since 2018, baloxavir has been approved for therapeutic and prophylactic use against influenza infection in otherwise healthy individuals aged [greater than or equal to] 12 years in numerous countries. Members of the AVWG discussed sequence-based and phenotypic methods for monitoring susceptibility to baloxavir and suggested that national influenza centres (NICs) gradually adopt sequence-based assays for monitoring susceptibility to baloxavir. To facilitate genotypic analysis of virus susceptibility to antivirals, AVWG members summarized published literature and prepared 3 reference tables listing NA and PA amino acid substitutions that were identified clinically or experimentally and analysed for their impact on susceptibility to NAIs (2,3) and baloxavir. (4) AVWG members will further review the guidance for NICs and update the protocols for monitoring and interpreting susceptibility to baloxavir. AVWG members also considered developing virtual training materials for NICs.

Review of external quality assessment programme (EQAP) panels

The antiviral panel was introduced in 2013 as an optional component of EQAPs to evaluate the ability of NICs to identify influenza variants with potentially reduced susceptibility to approved antiviral agents. The 2021 global EQAP antiviral panel contained (i) an A(H1N1)pdm09 sample containing a NA-H275Y/H mixture in which the NA-H275Y can confer highly reduced inhibition by oseltamivir when present in a high proportion, (ii) an A(H1N1)pdm09 virus containing the PA-I38T substitution associated with reduced susceptibility to baloxavir but with normal inhibition by NAIs and (iii) a wild-type influenza B/Victoria virus usually inhibited by both NAIs and baloxavir. The A(H1N1)pdm09 specimen encoding PA-I38T substitution was included for preparedness purposes,...

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Gale Document Number: GALE|A699771542