Highly Virulent Getah Virus Subgroup GIII-c Emerging in Pigs in China

Getah virus (GETV) is an emerging mosquito-borne zoonotic alphavirus that poses a threat to multiple animal species, particularly pigs, and carries significant public health implications. Nevertheless, the molecular evolution and pathogenicity of circulating GETV strains in China remain incompletely defined. In this study, three GETV strains were isolated from diseased piglets during concurrent outbreaks on three geographically distinct commercial pig farms in China in August 2025. The isolates shared 99.67%-99.91% genomic nucleotide (nt) identity and were phylogenetically classified into subgroup GⅢ-c. Amino acid sequence alignment against 136 reference strains from the GenBank database identified four substitutions in Nsp1 and Nsp3 that were absent from all reference strains, along with six conserved residues largely concentrated in a distinct subclade formed by the three isolates and five related reference strains. Pathogenicity evaluation using a representative isolate (GETV-YY/2025) in 7-day-old piglets revealed that the infected animals developed severe clinical signs, including fever, diarrhea, ataxia, and hindlimb paralysis, with a high mortality rate of 77.8% (7/9). The strain exhibited broad tissue tropism, with high viral loads detected in pharyngeal and rectal swabs, serum, and multiple visceral organs as early as 1 day postinoculation, accompanied by obvious cerebral vascular congestion and pulmonary hemorrhage. Notably, efficient contact transmission to sentinel piglets was observed, resulting in one fatality among the three contact animals (33.3%). Collectively, these findings characterize the emergence of a highly virulent GETV subgroup GⅢ-c circulating in Chinese pig populations, highlighting its capacity for efficient contact transmission and severe pathogenesis in neonatal pigs. This study provides critical insights into the evolutionary dynamics of GETV and informs the urgent development of prevention and control strategies against this re-emerging veterinary pathogen.