Virulent Newcastle disease virus (NDV), particularly emerging isolates, poses a major threat to poultry health and production, causing severe morbidity, high mortality, and economic losses. While ancestral class II genotypes II and IX have persisted globally across various bird species, the status of genotype IV NDV—last reported in India in 2000—had been uncertain. This study documents the emergence of genotype IV isolates in wild and domestic birds across China from 2021 to 2023, marking their return after more than two decades of presumed extinction. The representative isolate, KS02, showed severe lethality and high transmissibility in chicks compared to the circulating virus. The LaSota vaccine conferred complete protection against this isolate only when HI titers were at least twofold above the conventional protective threshold. These findings underscore the significant risk posed by reemerging genotype IV NDV, highlighting the urgent need for surveillance and updated vaccination strategies.

Ebola virus (EBOV) has caused severe outbreaks of haemorrhagic fever in Central and West Africa since the first observed zoonotic epidemic in the late 1970s. While recent outbreaks have revealed much ...