Volume 29, Number 7—July 2023
Research
Long-Term Epidemiology and Evolution of Swine Influenza Viruses, Vietnam
Jonathan Cheung, Anh Ngoc Bui, Sonia Younas, Kimberly M. Edwards, Huy Quang Nguyen, Ngoc Thi Pham, Vuong Nghia Bui, Malik Peiris1
, and Vijaykrishna Dhanasekaran1
, and Vijaykrishna Dhanasekaran1
Table 2
Seroprevalence against representative swine influenza A viruses isolated from Van Phuc slaughterhouse in Vietnam, 2010–2019*
| HA lineage | Reference antigen | No. (%) seropositive† |
||
|---|---|---|---|---|
| 2013–2015, n = 320 | 2016–2019, n = 440 | Overall, n = 760 | ||
| 2009 pandemic H1N1 |
A/California/04/2009 (H1N1) |
57 (17.8) |
61 (13.9) |
118 (15.5)† |
| Pre-2009 human seasonal H1-δ–like |
A/swine/Hanoi/11-260/2019 (H1N2) |
43 (13.4) |
89 (20.2) |
132 (17.4)† |
| Pre-2009 human seasonal H1-δ1a |
A/swine/Hanoi/12-276/2019 (H1N2) |
0 |
36 (8.2) |
36 (4.7) |
| H1-TR |
A/swine/Hanoi/7-305/2016 (H1N2) |
10 (3.1) |
8 (1.8) |
18 (2.4) |
| 2004/05 human H3N2-origin |
A/swine/Hanoi/10-984/2018 (H3N2) |
49 (15.3) |
70 (15.9) |
119 (15.7) |
| Total positive | 126 (39.4) | 183 (41.6) | 309 (40.7) | |
*Seropositivity defined as hemagglutination inhibition assay titer ≥40. HA, hemagglutinin; TR, triple reassortant. †A total of 30 serum samples were positive for both A/California/04/2009 (H1N1) and A/swine/Hanoi/11–260/2019 (H1N2). Because cross reactivity between these viruses is low, this result likely indicates sequential infections.
1These senior authors contributed equally to this article.
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