Did singing together spread coronavirus to four choirs?

In Amsterdam, 102 members of one choir fell ill, and cases have been reported in Europe, America and the UK. But scientists cannot agree on the cause

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On 8 March this year, the Amsterdam Mixed Choir gave a performance of Bach's St John Passion in the city's Concertgebouw auditorium. It was one of the last major classical concerts to be held in the Netherlands before the country went into Covid-19 lockdown.

The performance had unexpected consequences. Days later, singers began to sicken, one by one, until 102 of 130 choristers had fallen ill with Covid-19. One 78-year-old died, as did three partners of choir members; singers ended up in intensive care; and conductor Paul Valk displayed serious symptoms.