Joe Denly dismissed "a mild case of man flu" after posting his first century as an England player but emergency call-ups for Craig Overton and Dom Bess are proof that symptoms have hit the bowling attack harder.

England's first week in South Africa has veered wildly from the intended script, with Jofra Archer, Stuart Broad and Jack Leach all struck down by illness and yet to take the field in either warm-up match.

Five other players and staff have also been unwell, including Denly, but none badly enough to join the trio in lockdown at the team hotel. England have been concerned enough to draft in Somerset paceman Overton and his county colleague Bess just a few days before Christmas in a bid to swell their ranks ahead of the Boxing Day Test in Centurion.

On Friday, against South Africa A, Denly was not just fit but firing. He knocked up 103 in his side's 337 for five, the first time he has reached three figures for his country, albeit in a game that no longer carries first-class status after a request from the depleted tourists.

"I don't think I've had it quite as bad some of the boys, just a mild case of man flu I think," Denly said.

"It was fluey symptoms, bunged up, headaches... a bit under the weather. It was quite a sapping heat to be batting out there so I was a bit tired before the end but I've loaded up on medication and vitamins and I'm feeling alright."

The 33-year-old was better than alright for most of his time at the crease, striking 15 boundaries and putting together a chanceless stay until his late run out.

Ollie Pope was even more fluent as he raced to 70 not out, while Rory Burns (56), Ben Stokes (47) and Joe Root (12) were dropped four times between them.

Overton and Bess join up with the team on Saturday morning after an overnight flight, and could conceivably play some part over the course of the weekend, but England will be most keen to get Broad and Archer up and running.

"I suppose it's not ideal for those guys not to have taken part in these games but hopefully they've rested up well," said Denly.

"I don't know, you'd have to ask the doctor, but they're certainly on the mend and getting better each day. We'll see, but they've all played enough cricket and hopefully they can come back strong over the next couple of days."

Denly's top score in his 10 Test appearances is the 94 he made at The Oval in the last game of this summer's Ashes, making an otherwise low-key tour match a memorable occasion.

"It was nice to get that first one," he said. "It might not be a Test match but a hundred is a hundred."