The broadcaster, 56, explained how he feels he possibly caught the COVID-19 Delta variant at the 2020 Euros soccer finals at London's Wembley Stadium earlier in July.
Morgan detailed how he started to feel sick two days after attending the game, which was flooded with fans, and then a PCR test came back positive.
"My confidence that the event would be ‘covid safe’ had disintegrated," he said.
The former "Good Morning Britain" host received the Astra-Zeneca vaccine in the UK but still said he had symptoms which included fever, cold sweats, coughing and chest pain, which he called "alarming."
"This is definitely the roughest I've felt from any illness in my adult life, BUT, as I slowly come out the other side, coughing and spluttering, I'm still here — unlike so many millions around the world who've lost their lives to COVID in this pandemic," he wrote in Mail On Sunday newspaper.
"For that, I owe a heartfelt debt of thanks to the brilliant scientists up in Oxford who created the Astra-Zeneca vaccine with such astonishing speed," he wrote.
Morgan also tweeted out to his almost 8 million followers, "Yes… a salutary warning for everyone to be more careful than I was with this Delta variant flying around. And to get jabbed."