Radio DJ Colin Murray will be presiding over the Channel 4 quiz show as the team films new episodes while Nick shields at home during lockdown.
Colin is already known to Countdown audiences, having regularly sat in Dictionary Corner, alongside Susie Dent.
Nick announced the news on Twitter on Monday, revealing that in spite of the safety protocols show bosses have put in place to allow them to continue recording, his family have asked him to stay at home.
Writing on Twitter, he said: “Good luck to Colin Murray, popular dictionary corner guest and Countdown fanatic, who takes over from me as host today and for the rest of Covid lockdown recordings (although I’ll still be on your screens for a week or two) as this 76-year-old shields at home – in spite of the amazing military-style safety protocols put in place by ITV Studios and Channel 4.
“Between you and me, I’d have confidently carried on, but the family has handcuffed me to a radiator, saying ‘You’re not going anywhere’.”
Nick added: “So have fun Colin and keep my chair warm for me.”
Back in July, Nick praised the makers of Countdown for going to “such trouble” over the precautions, as his age makes him vulnerable to coronavirus.
The former Apprentice star began hosting the show in 2012, after taking over from Jeff Stelling.
Countdown airs weekdays at 2.15pm on Channel 4.