His HIV diagnosis "came out of the blue" but Andrew Bates is determined to show people that life does not come to an end.
Mr Bates is speaking out in the third of the AIDSfree appeal's 12 Days of Christmas messages because he does not want the fear of a positive diagnosis preventing people from taking a test for HIV.
The 25-year-old was diagnosed just over three years ago and he says in his message: "Even today there are a lot of misconceptions about HIV and this can lead to stigma.
"Now this prevents people from being tested, getting diagnosed and getting the right treatment that they need to essentially save their lives.
"Today I live healthily and I challenge my own stigma through running.
"I ran a half marathon for the Terrence Higgins Trust to show people that despite living with HIV I was still healthy and happy."
Mr Bates said he now belonged to a running club and competed in races.
He continued: "I am more determined than ever to show people that life does not have to end after an HIV diagnosis."
Donating to the Evening Standard's AIDSfree appeal, which is supporting the Elton John Aids Foundation, would help people like Mr Bates around the world get the support they needed, he added.
Mr Bates is the third of our 12 Days of Christmas messengers, joining James Corden and Victoria Beckham in urging people to donate to the appeal.
The 12 Days of Christmas series features a message from a high-profile backer or HIV campaigner each day pledging support for our campaign through to Christmas Eve.
