Avian paramyxovirus type 1-associated severe pneumonia in humans: Molecular characterization and zoonotic transmission risk.

Background: Avian paramyxovirus serotype 1 (APMV-1, Newcastle disease virus) is a major poultry pathogen. Human infections are rare and typically self-limiting, but its potential to cause severe respiratory disease and the mechanisms underlying cross-species transmission remain understudied. Methods: We analyzed a 65-year-old male with severe pneumonia who had contact with sick backyard feeder chickens. Immunocompetence was evaluated via routine blood tests and serum immunoglobulin levels. mNGS identified 40 APMV-1 sequence reads (50.6% microbial abundance) covering 10.78% of the genome. APMV-1 nucleic acid, antigen, and high IgG titers were detected in human specimens. High viral loads were confirmed in chicken and environmental samples. Phylogenetic analysis classified the strain as Class I genotype 1.1.2 1b, genetically identical to poultry-derived viruses, suggesting a potential avian-to-human transmission. Results: mNGS identified 40 APMV-1 sequence reads (50.6% microbial abundance) covering 10.78% of the genome. APMV-1 nucleic acid, antigen, and high IgG titers were detected in human specimens. High viral loads were confirmed in chicken and environmental samples. Phylogenetic analysis classified the strain as Class I genotype 1.1.2 1b, genetically identical to poultry-derived viruses, providing molecular clues for zoonotic infection. Conclusions: APMV-1 Class I genotype 1.1.2 1b can cross the species barrier and cause life-threatening pneumonia in immunocompetent humans. Our findings highlight its underrecognized zoonotic potential, emphasizing the need for enhanced surveillance in avian and human populations and research into determinants of cross-species pathogenicity.