July 2023 - Avian influenza A(H 5N1) and the continuing outbreak

Introduction In late 2021, a strain of highly pathogenic avian influenza (HPAI), commonly referred to as bird flu, began spreading among wild and farmed birds globally.1 The outbreak, caused by influenza A(H5N1) persisted through 2022 and into 2023, and has resulted in deaths of wild birds and culling of millions of poultry birds across Canada over the past two years. [...] While the risk to humans remains low, the persistence of the current outbreak, the spread among a wide range of bird and mammal species, and threat of the virus AVIAN INFLUENZA A(H5N1) AND THE CONTINUING OUTBREAK 2 becoming endemic in the Americas warrants a fresh look at the current situation, including the types of measures a One Health approach encompasses to mitigate the impacts of the outbrea. [...] Ongoing and recurring events have been observed in Europe, Asia, the Americas, and Africa throughout the first half of 2023,6 in the most widespread and persistent outbreak of HPAI ever seen.14 Transmission to animals and humans This section summarizes current reports on infections among wildlife, poultry, and humans and how the virus transmits to hosts (Boxes 1–4). [...] The European Centres for Disease Control and Prevention (ECDC) thus published guidance on enhanced surveillance of avian influenza infection in hospital settings in June 2023.49 The persistence of the virus in wildlife and recurrence of outbreaks globally, presents additional risks during the migratory bird season in North America later in 2023. [...] AVIAN INFLUENZA A(H5N1) AND THE CONTINUING OUTBREAK 12 Conclusions The persistence of the current A(H5N1) outbreak has demonstrated an ability of the virus to reassort, evolve, and acquire additional mutations that has led to persistence of the virus and infection of a wider diversity of bird and mammal spe.