Worryingly, the news comes after Laurence performed during Tuesday's opening semi-final where he sang his new song 'Feel Something'.
The Dutch singer won the last competition in 2019 with his song 'Arcade' and had been due to return and perform at the 2021 final in Rotterdam this weekend.
However, on Thursday morning, it was announced that Laurence had tested positive for COVID-19 and would not be able to perform at the event.
While Laurence had "mild symptoms", the seven-day minimum isolation period meant he would miss the final.
The singer had tested negative on Monday, 17 May and, therefore, was able to perform at the first semi-final.
Laurence's management said that he was "very disappointed" not to return and perform in the final.
A statement from Eurovision executive producer Sietse Bakker reads: "We are of course disappointed, first of all for Duncan, who deserves a live performance on our very own Eurovision stage after his 2019 victory and the worldwide success of Arcade.
"Of course, we wish Duncan a speedy recovery."
There is a big worry here, especially given the fact that Laurence would have mixed with this year's contestants during his live semi-final performance, which you can watch below.
In mirror-like circumstances, Daði og Gagnamagnið, Iceland's entry for the contest were forced to pull out of the live shows after a band member tested positive for COVID-19.
Saturday's final is still going ahead with strict safety measures in place to ensure that the contestants can compete safely in the in-person competition.
Everyone working on the show must test negative for coronavirus in order to take part.
The Eurovision Song Contestant takes place Saturday, 22 May at 8pm on BBC One.
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