Jack Leach contracted sepsis in New Zealand late last year and has also been struck by illness since arriving in South Africa.
South Africa great AB de Villiers retired from international cricket in May 2018, but he is hoping to make a Proteas return.
With James Anderson ruled out of the remainder of the series, England must weigh up who to bring in for the third Test against South Africa.
The use of stump mics has been questioned by Jos Buttler, who apologised for his expletive-laden outburst at Vernon Philander.
Illness and injury have affected England during their tour of South Africa and Joe Root has been struck by illness again.
England have lost James Anderson for the rest of the South Africa tour but are set to be boosted by the return of Mark Wood.
Joe Denly is yet to hit a Test hundred for England, but the 33-year-old believes it is only a matter of time until he reaches a big score.
Despite losing the second Test to England, South Africa are unchanged for the last two matches of the series.
England opener Zak Crawley is hopeful he has done enough to earn a spot in Joe Root's side for the third Test against South Africa.
England wicketkeeper-batsman Jos Buttler has been punished for the verbal volleys he threw at Vernon Philander.