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Volume 32, Number 6—June 2026

Dispatch

Concurrent Detection of Swine-Origin Influenza A(H1N1) Virus in Pigs and Farmer, Switzerland

Jonas Steiner1, Mike Mwanga1, Larise Oberholster, Matthias Licheri, Manon F. Licheri, Heiko Nathues2, Ronald Dijkman2, and Jenna N. Kelly2Comments to Author 
Author affiliation: University of Bern Multidisciplinary Center for Infectious Diseases, Bern, Switzerland (J. Steiner, M. Mwanga, L. Oberholster, M. Licheri, M.F. Licheri, H. Nathues, R. Dijkman, J.N. Kelly); University of Bern Vetsuisse Faculty, Bern (J. Steiner, M. Mwanga, H. Nathues, J.N. Kelly); University of Bern Faculty of Medicine, Bern (M. Mwanga, L. Oberholster, M. Licheri, M.F. Licheri, R. Dijkman); Institute of Virology and Immunology, Bern and Mittelhäusern, Switzerland (M. Mwanga, J.N. Kelly)

Main Article

Table 2

Comparison of amino acid sequences in the hemagglutinin antigenic region of swine H1N1, human seasonal H1N1, and seasonal vaccine strains in study of influenza A(H1N1) virus in pigs and farmer, Switzerland, November 2023*

Isolate
 HA-H1 residue positions
Antigenic site Sa 124 125 153 154 155 156 157 159 160 161 162 163 164
Vaccine A/Wisconsin/67/2022 P N K K G K S P K I N Q T
Vaccine A/Victoria/4897/2022/H1N1 P N K K G K S P K I N Q T
Study A/Switzerland/H0001/2023/H1N1 P N K K G N A P K I R K S
Human seasonal H1N1
 P
 N
 K
 K
 G
 K
 S
 P
 K
 I
 N
 Q
 T
Antigenic site Sb 184 185 186 187 188 189 190 191 192 193 194 195
Vaccine A/Wisconsin/67/2022 T I T D Q E S L Y Q N A
Vaccine A/Victoria/4897/2022/H1N1 T I T D Q E S L Y Q N A
Study A/Switzerland/H0001/2023/H1N1 T D S D Q Q T L Y Q N N
Human seasonal H1N1
 T
 I
 T
 D
 Q
 E
 S
 L
 Y
 Q
 N
 A
Antigenic site Ca1 166 167 168 169 170 203 204 205 235 236 237
Vaccine A/Wisconsin/67/2022 I N D K G T S R E P G
Vaccine A/Victoria/4897/2022/H1N1 I N D K G T S R E P G
Study A/Switzerland/H0001/2023/H1N1 T N N K G S S K D Q G
Human seasonal H1N1
 I
 N
 D
 Q
 G
 T
 S
 R
 E
 P
 G
Antigenic site Ca2 137 138 139 140 141 142 221 222
Vaccine A/Wisconsin/67/2022 S H A G A R R D
Vaccine A/Victoria/4897/2022/H1N1 S H A G A R R D
Study A/Switzerland/H0001/2023/H1N1 S H S G T K R E
Human seasonal H1N1
 P
 H
 A
 G
 A
 K
 R
 D
Antigenic site Cb 70 71 72 73 74 75
Vaccine A/Wisconsin/67/2022 L S T A R S
Vaccine A/Victoria/4897/2022/H1N1 L S T A R S
Study A/Switzerland/H0001/2023/H1N1 L L T A D S
Human seasonal H1N1 L S T A R S

*Comparison of amino acid sequences in the antigenic region among the human 2023–24 seasonal vaccine strains, the swine H1N1 (swH1N1) virus identified in this study, and a representative human seasonal H1N1 virus. Numbering is based on the recommended HA-H1 numbering scheme using the HA Subtype Numbering Conversion tool (https://www.bv-brc.org/app/HASubtypeNumberingConversion). Orange shading denotes mutations distinguishing the vaccine strain from the study swine H1N1 virus. Gray shading indicates mutations distinguishing the vaccine strain from the representative human seasonal virus. A, alanine; D, aspartic acid; E, glutamic acid; G, glycine; H, histidine; HA, hemagglutinin; I, isoleucine; K, lysine; L, leucine; N, asparagine; P, proline; Q, glutamine; R, arginine; S, serine; T, threonine; Y, tyrosine.

Main Article

1These first authors contributed equally to this article.

2These senior authors contributed equally to this article.

Page created: April 27, 2026
Page updated: June 01, 2026
Page reviewed: June 01, 2026
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