Eurosurv. Investigation of an international water polo tournament in Czechia as a potential source for early introduction of the SARS-CoV-2 Omicron va

[tetano]

• Christoph Rudin[SUP]1,*[/SUP] , Nena Bollen[SUP]2,*[/SUP] , Samuel L Hong[SUP]2[/SUP] , Fanny Wegner[SUP]3,4[/SUP] , Lida Politi[SUP]5,6[/SUP] , Kassiani Mellou[SUP]7[/SUP] , Caspar Geenen[SUP]8[/SUP] , Sarah Gorissen[SUP]8[/SUP] , Bruno Verhasselt[SUP]9[/SUP] , Keith Durkin[SUP]10[/SUP] , Coralie Henin[SUP]11[/SUP] , Anne-Sophie Logist[SUP]2[/SUP] , Simon Dellicour[SUP]2,12[/SUP] , Tobias Resa[SUP]13[/SUP] , Tanja Stadler[SUP]14,15[/SUP] , Piet Maes[SUP]2[/SUP] , Lize Cuypers[SUP]8,16[/SUP] , Emmanuel André[SUP]8,16[/SUP] , Adrian Egli[SUP]3,4,17,18,**[/SUP] , Guy Baele[SUP]2,**[/SUP]

Background

The earliest recognised infections by the SARS-CoV-2 Omicron variant (Pango lineage B.1.1.529) in Belgium and Switzerland suggested a connection to an international water polo tournament, held 12–14 November 2021 in Brno, Czechia.

Aim

To study the arrival and subsequent spread of the Omicron variant in Belgium and Switzerland, and understand the overall importance of this international sporting event on the number of infections in the two countries.

Methods

We performed intensive forward and backward contact tracing in both countries, supplemented by phylogenetic investigations using virus sequences of the suspected infection chain archived in public databases.

Results

Through contact tracing, we identified two and one infected athletes of the Belgian and Swiss water polo teams, respectively, and subsequently also three athletes from Germany. In Belgium and Switzerland, four and three secondary infections, and three and one confirmed tertiary infections were identified. Phylogenetic investigation demonstrated that this sporting event played a role as the source of infection, but without a direct link with infections from South Africa and not as a superspreading event; the virus was found to already be circulating at that time in the countries involved.

Conclusion

The SARS-CoV-2 Omicron variant started to circulate in Europe several weeks before its identification in South Africa on 24 November 2021. Accordingly, it can be assumed that travel restrictions are usually implemented too late to prevent the spread of newly detected SARS-CoV-2 variants to other regions. Phylogenetic analysis may modify the perception of an apparently clear result of intensive contact tracing.



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https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.45.2300018