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Volume 32, Number 2—February 2026

Dispatch

Avian Influenza A(H9N2) Virus Transmission across Chicken Production and Distribution Networks, Vietnam

Mathew HennesseyComments to Author , Thuy Hoang Thi, Jayna Raghwani, Younjung Kim, Hoa Thi Thanh Pham, Trang Huyen Nguyen, Hung Quoc Nguyen, Joshua G. Lynton-Jenkins, Ashley C. Banyard, Ian H. Brown, Joe James, Tom Lewis, Nicola S. Lewis, Dirk Pfeiffer, Fiona Tomley, Damer Blake, Ngoc Pham Thi, Anne Conan, Vuong Nghia Bui1, and Guillaume Fournié1
Author affiliation: Royal Veterinary College, London, UK (M. Hennessy, J. Raghwani, N.S. Lewis, D. Pfeiffer, F. Tomley, D. Blake, G. Fournié); National Institute of Veterinary Research, Hanoi, Vietnam (T.H. Thi, T.H. Nguyen, H.Q. Nguyen, N.P. Thi, V.N. Bui); University of Oxford, Oxford, UK (Y. Kim); Université de Montpellier, Montpellier, France (H.T.T. Pham, A. Conan); World Organisation for Animal Health/Food and Agriculture Organization International Reference Laboratory for Avian Influenza Animal and Plant Health Agency, Addlestone, UK (J.G. Lynton-Jenkins, A.C. Banyard, J. James, T. Lewis); Pirbright Institute, Pirbright, UK (I.H. Brown); World Health Organization Collaborating Centre for Influenza Reference and Research, London (N.S. Lewis); City University, Hong Kong, China (A. Conan); French Agricultural Research Centre for International Development, Harare, Zimbabwe (A. Conan); Université de Lyon, Marcy l’Etoile, France (G. Fournié); Université Clermont Auvergne, Saint Genes Champanelle, France (G. Fournié)

Main Article

Figure 1

Geographic area and sites for study of avian influenza virus A(H9N2) prevalence across chicken production and distribution networks, Bac Giang, Hanoi, Hai Duong, and Quang Ninh Provinces, Vietnam, March 2021–March 2022. The 4 study provinces and the individual sites (farms and distribution facilities) are shown alongside the detection of avian influenza viruses (contaminated defined as >1 positive sample; noncontaminated defined as all samples testing negative) and the spatiotemporal cluster of contaminated farms. The 2 other farms that appear located in the cluster were not sampled during the temporal window.

Figure 1. Geographic area and sites for study of avian influenza virus A(H9N2) prevalence across chicken production and distribution networks, Bac Giang, Hanoi, Hai Duong, and Quang Ninh Provinces, Vietnam, March 2021–March 2022. The 4 study provinces and the individual sites (farms and distribution facilities) are shown alongside the detection of avian influenza viruses (contaminated defined as >1 positive sample; noncontaminated defined as all samples testing negative) and the spatiotemporal cluster of contaminated farms. The 2 other farms that appear located in the cluster were not sampled during the temporal window.

Main Article

1These authors contributed equally to this article.

Page created: January 29, 2026
Page updated: February 19, 2026
Page reviewed: February 19, 2026
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