South Africa v England: Yorkshire's Gary Ballance on standby after Alex Hales is hit by bug

Reserve seam bowler Chris Jordan and batsman Nick Compton have already come through a sickness bug, while a number of the team’s families also suffered during the Cape Town Test, but the timing of Hales’s predicament is more worrying.

He was fit enough to net in Johannesburg yesterday, though England were concerned enough by his symptoms to ensure he did so away from the rest of the group.

The Nottinghamshire batsman would be expected to play unless his condition worsens overnight but Yorkshire’s Gary Ballance is on standby should he be needed.

In that instance, Compton, having opened the batting in his first nine Tests for England, would join captain Alastair Cook at the top of the order, with Ballance slotting into the middle order.

“Alex Hales has got a bit of a bug. He’s come for a hit and he’ll go back after that so he doesn’t infect the rest of us,” said Cook.

“We’ll have to wait and see on him, but he’s having a hit so he can’t be too bad.

“It seems to strike a bit randomly. Nick had it the other day and he’s fine.”

While Hales’s participation will be resolved by the time of the toss, there is a lingering worry that other members of the side could fall ill mid-match.

“You can’t do anything about it as a captain, the medical team are on it,” said Cook.

“It’s just a virus bug, so it’s hard to stop. If it happens in the game then it’s bad luck isn’t it?”

England go into the Test knowing victory would give them a decisive 2-0 lead with one to play.

The prize is a big one – with the Proteas ranked number one in the world and England having only won once on these shores since South Africa’s sporting readmission.

“It would be a great achievement for this side to come here and beat South Africa away from home. And we’re in a position to do that,” said Cook.

“The opportunity is there and it’s just whether we’re good enough to take it.

“It’s an exciting time to play on what are probably two result pitches in these next two games. We need to win one to win the series. That is a great situation to be in.”

South Africa will be led for the first time at the Wanderers by AB de Villiers, who inherited the reins when Hashim Amla resigned last week.

De Villiers promises to bring a more dynamic leadership style than his scholarly predecessor, and vowed to make the tourists feel the heat.

“I am a very competitive person and I truly hate losing,” he said. “Losing is not an option. We are here to win the series and that is all I am focussing on at the moment.

“I’ve never been the kind to throw a lot of words around or sledge but I like to have good body language and for the team to have good body language, to be in their face in that way.

“I like to really make them feel uncomfortable and to remind them they are away from home and not enjoying (the exchange rate of) the pound to the rand too much.”

South Africa have released spinner Dane Piedt from their squad, alongside batsman Rilee Rossouw, confirming they will go in with an all-out pace quartet. The hosts expect pace and bounce at the Wanderers and are ready to hand a debut to the rapid Hardus Viljoen on his home ground.

That leaves opener Dean Elgar as their only slow bowling option, and Cook is glad he has not had to confront the same dilemma, with all-rounders Ben Stokes and Moeen Ali always ensuring him an extra resource in the field.

“If the ball does fly through and seams around we have got a pretty good seam attack as well and if it does get warm and spins a little bit we have got that option too,” said Cook.