A Sport Relief celebrity challenge has been moved from Mongolia to Namibia because of concerns about coronavirus in neighbouring China.
Seven stars, including Frankie Bridge, Karim Zeroual, Nick Grimshaw and Samantha Womack, were due to take part in On Thin Ice in Mongolia next week.
They had been preparing for freezing temperatures and a 100-mile triathlon.
Instead, they are set to undertake a "gruelling four-day, 100-mile expedition" across the Namib Desert.
Comic Relief interim chief executive Ruth Davison said: "After closely monitoring travel advice, we have decided to relocate our international fundraising challenge, which starts this weekend.
"We had previously been looking at a range of locations and challenges and we think that the Namib Desert expedition is a fitting alternative.
"We are extremely grateful for our team of celebrities who have not wavered in their passion and determination to want to take on a challenge for us, which is extraordinary in itself."
Grimshaw told his BBC Radio 1 listeners: "It's still great to do it. However I can't work out if it's better or worse."
The challenge, to raise awareness and fundraise for mental health services, has been renamed Sport Relief: The Heat Is On.
The other famous faces taking part are Louise Minchin, Krishnan Guru-Murthy and Rob Rinder.
The team will start at the source of the Kuiseb River and travel on foot and on bike towards the Skeleton Coast.
They will scale the highest sand dunes in the world in temperatures up to 30C.
A BBC One documentary following the fundraiser will be shown in the run up to Sport Relief on 13 March.
Sport Relief, which takes place every two years, is a fundraising campaign run by Comic Relief that aims to raise money to tackle issues such as mental health stigma, domestic abuse, homelessness and poverty, both in the UK and around the world.
The last time it was held, it had raised £38m for charitable causes by the end of its live TV show.