Avian influenza overview September – December 2021. - Adlhoch, Cornelia; Fusaro, Alice; Gonzales, José L; Kuiken, Thijs; Marangon, Stefano; Niqueux, Éric; Staubach, Christoph; Terregino, Calogero; Aznar, Inma; Muñoz Guajardo, Irene; Baldinelli, Francesca (EFSA Journal, 2021)