The article first appeared on the UK satirical website, NewsBiscuit, at the end of November.
It was then published by Zimbabwe’s Standard on Sunday and picked up by the SpyGhana news website on Tuesday.
NewsBiscuit said their site kept crashing on Wednesday because of increased hits from Africa.
“We’ve had half as many visitors from Africa in the last few days as we’d expect generally in a whole month,” comic writer John O’Farrell from NewsBiscuit told the BBC.
He said the story had been viewed more than 50,000 times in the last few days, about 20 times more than is usual.
The spoof article said that the boxer would now be known as Michelle and was feeling fine after undergoing a 16-hour operation.
An online search also shows that the Zambian news website Zambia Watchdog carried the story on Monday, with the headline “Mike Tyson sex change operation ‘a complete success’, say surgeons”, but the link now says the page cannot be displayed.
Mr O’Farrell says the story was initially posted on NewsBiscuit’s writers’ board – the website team then put a photo on it and added it to their front page on 30 November.
It is not the first time a NewsBiscuit article has been taken seriously in Africa, he says.
In 2007, a story about Ghana’s former President, John Kufuor, failing to notice the flags lining his route to Buckingham Palace during a visit to the UK caused outrage in the Ghanaian press, he said.
Last month, the online version of the Chinese Communist Party’s official newspaper also appeared to fall for a spoof story by the US satirical website, The Onion.
The People’s Daily ran a 55-page photo spread of North Korean leader Kim Jong-un after he was declared The Onion’s Sexiest Man Alive for 2012.