England are waiting on the fitness of Alex Hales for the third Test against South Africa, captain Alastair Cook has revealed.
Cook's opening partner, who made 60 in the first innings of the second Test in Cape Town, has become the latest member of the party to be struck down by a stomach bug.
Nick Compton, who has recovered from a similar ailment, would most likely step up to open in Johannesburg on Thursday should Hales not make it, with Yorkshire's Gary Ballance slotting into the middle order.
"Alex Hales had a bug yesterday and today," said Cook.
"You can't do anything about it as a captain, the medical team are on it. Hopefully he'll be fine.
"It seems to strike randomly, Nick had it the other day - he's fine."
Cook has cautioned England not to get ahead of themselves as they seek to wrap up the series.
The tourists lead 1-0 with two Tests remaining, h aving comprehensively won the opener in Durban before an entertaining draw in Cape Town.
And Cook said: "We're in a really good position and it's an exciting time to play, on probably two result wickets for these two games.
"We need to win one of them to win the series. It's a great position to be in, we've played some good cricket so far on tour, but the danger of saying you only need to win one is you start looking too far ahead.
"We need to do a lot of good things to put pressure on South Africa and win the game. The results will look after themselves if we play well."