— since december 2021, 10 human cases of avian influenza h5n1 (of clade 2.3.4.4b) have been reported globally and between 1 october 2022 and 31 may 2023, influenza h5n1. — the highly pathogenic strain of bird flu, clade 2.3.4.4b h5n1, has swept through bird populations and other wildlife in the us, europe and asia, wreaking havoc on poultry and.