14 May 2026
A new study reports the first-ever H9N2 outbreak in Darwin’s rhea in the Peruvian Andes.
Avian influenza viruses of the H9N2 subtype typically cause only mild disease. However, scientists recognize this strain as a major “gene donor,” frequently exchanging genetic segments with highly pathogenic viruses such as H5N1 and H7N9, thereby facilitating the emergence of novel genotypes with pandemic potential. Although evidence of H9N2 circulation in South America has previously been limited, this outbreak in Peru suggests a significant shift in the regional ecology of the virus.
Between June and July 2025, a severe outbreak struck a remote conservation center in Puno, Peru, located more than 4,000 meters above sea level. The outbreak affected the “Suri” (Rhea pennata), a large flightless bird species classified as critically endangered by the Peruvian government.
A research team led by Mariana Leguia conducted whole-genome sequencing to characterize the virus. The analysis identified the strain as a North American-origin Low Pathogenicity Avian Influenza (LPAI) virus, representing the third independent introduction of H9 viruses into South America. Although LPAI viruses are generally restricted to the respiratory and intestinal tracts, this strain disseminated systemically throughout the birds’ bodies. Pathological examinations revealed severe inflammation in the liver, lungs, and even the brain. Genetic analysis also identified mammalian-adaptation mutations previously associated with increased virulence and enhanced replication in mammalian hosts.
This finding carries implications far beyond the conservation of the Suri. Peru has one of the highest per-capita chicken consumption rates in the world, making the poultry sector critical to national food security. The occurrence of this outbreak in such an isolated, high-altitude region suggests that migratory wild birds along the Pacific Flyway may be acting as silent carriers of the virus.
Garcia-Glaessner et al. (2026). Outbreak of H9N2 avian influenza viruses in lesser rhea in Peru, June–July 2025. bioRxiv.
