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Avian influenza A(H5) virus circulation in live bird markets in Vietnam, 2017–2022
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  • Diep Nguyen,
  • Kelsey Sumner,
  • Thoa Nguyen,
  • Minh Phan,
  • Tien Hoang,
  • Chuong Vo,
  • Tho Nguyen,
  • Phuong Nguyen,
  • Genyan Yang,
  • Yunho Jang,
  • Joyce Jones,
  • Sonja Olsen,
  • Philip Gould,
  • Long Nguyen,
  • C. Todd Davis
Diep Nguyen
Department of Animal Health
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Kelsey Sumner
Centers for Disease Control and Prevention

Corresponding Author:rhq3@cdc.gov

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Thoa Nguyen
Centers for Disease Control and Prevention
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Minh Phan
Department of Animal Health
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Tien Hoang
Department of Animal Health
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Chuong Vo
Department of Animal Health
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Tho Nguyen
National Center for Veterinary Diagnosis
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Phuong Nguyen
Regional Animal Health Officer number 6
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Genyan Yang
U.S. Centers for Disease Control and Prevention
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Yunho Jang
Centers for Disease Control and Prevention
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Joyce Jones
Centers for Disease Control and Prevention
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Sonja Olsen
Centers for Disease Control and Prevention
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Philip Gould
Centers for Disease Control and Prevention
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Long Nguyen
Department of Animal Health
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C. Todd Davis
CDC
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Abstract

Background: Highly pathogenic avian influenza A(H5) human infections are a global concern, with many A(H5) human cases detected in Vietnam, including a case in October 2022. Using avian influenza virus surveillance from March 2017‒September 2022, we described the percent of pooled samples that were positive for avian influenza A, A(H5), A(H5N1), A(H5N6), and A(H5N8) viruses in live bird markets in Vietnam. Methods: Monthly at each LBM, 30 poultry oropharyngeal swab specimens and five environmental samples were collected. Samples were pooled in groups of five and tested for influenza A, A(H5), A(H5N1), A(H5N6), and A(H5N8) viruses by real-time reverse-transcription polymerase chain reaction. Trends in the percent of pooled samples that were positive for avian influenza were summarized by LBM characteristics and time and compared to the number of passively detected avian influenza outbreaks using Spearman’s rank correlation. Results: A total of 25,774 pooled samples were collected through active surveillance at 167 LBMs in 24 provinces; 36.9% of pooled samples were positive for influenza A, 3.6% A(H5), 1.9% A(H5N1), 1.1% A(H5N6), and 0.2% A(H5N8). Influenza A(H5) viruses were identified January–December and at least once in 91.7% of sampled provinces. In 246 A(H5) outbreaks in poultry; 20.3% were influenza A(H5N1), 60.2% A(H5N6), and 19.5% A(H5N8); outbreaks did not correlate with active surveillance. Conclusions: In Vietnam, influenza A(H5) viruses were detected by active surveillance in LBMs year-round and in most provinces sampled. In addition to outbreak reporting, active surveillance for A(H5) viruses in settings with high potential for animal-to-human spillover can provide situational awareness.
18 Sep 2023Submitted to Influenza and other respiratory viruses
19 Sep 2023Submission Checks Completed
19 Sep 2023Assigned to Editor
03 Oct 2023Reviewer(s) Assigned
17 Oct 2023Review(s) Completed, Editorial Evaluation Pending
05 Nov 2023Editorial Decision: Revise Minor