Résumé
High-pathogenicity avian influenza A subtype H5N1 viruses of the Goose/Guangdong/1/96 lineage and low pathogenicity avian influenza A subtype H9N2 viruses are endemic in Southeast Asia, including Vietnam. Both subtypes affect poultry production and pose zoonotic risks (1) directly and through their involvement in the generation of novel virus reassortments (2). In Vietnam, the subtypes are frequently detected in live bird markets, and higher prevalence is associated with practices such as mixing poultry from multiple sources (3). However, that finding should be interpreted cautiously because farms and the markets they supply have limited prevalence data, and the focus on markets has diverted attention from larger slaughter facilities despite those facilities playing a key role in poultry distribution. Together, those gaps constrain understanding of avian influenza virus (AIV) transmission risk along the production and distribution network (PDN) through which poultry are raised, traded, and consumed. We conducted a cross-sectional study in northern Vietnam to assess avian influenza A(H5N1) and A(H9N2) prevalence in chickens, determine how AIV prevalence varied between farms and the different distribution facility types, and examine how viral genetic diversity was structured along the PDN.</p></div> <div>The Study<p>We selected 50 farms and 52 distribution facilities, including retail and wholesale markets, small-scale slaughter points, and industrial slaughterhouses, across 4 provinces (Bac Giang, Ha Noi, Hai Duong, and Quang Ninh) (Figure 1). We identified distribution facilities trading or processing slowgrowing colored broiler chickens (i.e., hybrids of indigenous roosters and fast-growing broiler hens that account for most chicken meat produced in Vietnam [4]) through consultation with provincial