“…Although the host range for HPAI H5Nx are known to be broad based on challenge studies and wild-bird surveillance (Lee et al 2017, Empress-i 2023), virulence and transmissibility appear to be highly variable across taxa. Mass mortality events attributed to H5 clade 2.3.4.4b have been recorded in several groups such as wildfowl, shorebirds, seabirds, and raptors (Abolnik et al 2023, Adlhoch & Baldinelli 2023, Lane et al 2023, Pohlmann et al 2023), whereas in other groups, such as passerines, such reports are lacking. However, passerines have demonstrated moderate to high seroprevalence against older clades of HPAI H5Nx, likely indicative of past infection (Kou et al 2005, Kaplan & Webby 2013), and detecting increased mortality in these less conspicuous species is likely to be more difficult.…”