Characterization of H7N6 HPAI virus in South African poultry, 2023
In 2023, South Africa reported the emergence of a high pathogenicity avian influenza (HPAI) H7N6 virus in poultry, marking the first documented H7 HPAI outbreak on the African continent. The virus caused significant mortality and economic losses, particularly in egg-laying and broiler breeder flocks, and subsequently spread to neighboring Mozambique. A study published in Transboundary and Emerging Diseases sequenced the complete genomes of 68 H7N6 isolates and traced their phylogenetic origin to a reassortment of influenza viruses circulating among southern African wild birds. Molecular clock analysis indicated that the virus emerged in early May 2023, initially affecting smallholder flocks before spreading to commercial farms in June.
The H7N6 virus acquired a multibasic cleavage site via nonhomologous recombination with host ribosomal RNA, potentially accelerating its pathogenic evolution. Although it spread efficiently among commercial operations, the virus exhibited moderate pathogenicity in chickens, with an IVPI of 1.67 and variable mortality. Genetic markers indicated negligible zoonotic risk, and no human cases were reported. High viral loads detected in aerosols, feces, feathers, and feather dust likely facilitated rapid farm-to-farm transmission, though the exact pathways remain unclear.
