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Abstract

In week 33, 2025, the integrated respiratory virus surveillance at Statens Serum Institut, Denmark, detected an atypical sixfold increase in influenza A(H1N1)pdm09 cases. Rapid sequencing of viruses collected in week 33 identified a highly related cluster of 17 cases. Telephone interviews with patients belonging to this cluster revealed that they all had attended a large open-air music festival. This is the first time an influenza outbreak has been detected during the summer in Denmark related to a large gathering.

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/content/10.2807/1560-7917.ES.2025.30.36.2500658
2025-09-11
2026-04-14
/content/10.2807/1560-7917.ES.2025.30.36.2500658
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References

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An interseasonal outbreak of influenza A(H1N1)pdm09 related to a music festival, Denmark, August 2025
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Amanda+Bolt+Botnen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bolt Botnen Amanda</a>, <a href="/search?value1=Hanne-Dorthe+Emborg&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Emborg Hanne-Dorthe</a>, <a href="/search?value1=Casper+Thorup&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Thorup Casper</a>, <a href="/search?value1=Jesper+Krog&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Krog Jesper</a>, <a href="/search?value1=Sofia+Myrup+Otero&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Myrup Otero Sofia</a>, <a href="/search?value1=Stine+Nielsen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Nielsen Stine</a>, <a href="/search?value1=Bolette+S%C3%B8borg&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Søborg Bolette</a>, <a href="/search?value1=Ramona+Trebbien&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Trebbien Ramona</a></span>. An interseasonal outbreak of influenza A(H1N1)pdm09 related to a music festival, Denmark, August 2025. <a href="/content/ecdc">Euro Surveill.</a> 2025;30(36):pii=2500658. <a href="https://doi.org/10.2807/1560-7917.ES.2025.30.36.2500658" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2025.30.36.2500658</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 27 Aug 2025;&nbsp;&nbsp; <span class="generated">Accepted</span>: 09 Sept 2025 </span> </p>
/content/10.2807/1560-7917.ES.2025.30.36.2500658
/content/10.2807/1560-7917.ES.2025.30.36.2500658
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