England added two bowlers to their squad on Friday after illness struck the camp less than a week before the first test against hosts South Africa, the England and Wales Cricket Board said.
Seamer Craig Overton and off-spinner Dominic Bess will join the squad as cover ahead of the start of the four-test series, which begins on Boxing Day in Pretoria.
Bowlers Jofra Archer, Stuart Broad and Jack Leach are among a host of squad members hit by 'flu-like' symptoms sweeping through the England camp.
Batsmen Joe Denly and fielding coach Carl Hopkinson were also suffering, officials said.
Bess, 22, played two tests against Pakistan in 2018 while 25-year-old Overton won the last of four caps in the Ashes in September. The Somerset duo are due to arrive in Johannesburg on Saturday.
The raft of sick players saw England request a downgrading of their three-match warm-up game against South Africa A at Willowmoore Park in Benoni, which began on Friday with England winning the toss and electing to bat.
The downgrading of the game offers the chance for the sick trio to still get in some bowling practice over the weekend before the start of the first test at Centurion next Thursday.
It is the last chance for the likes of Archer and Broad, expected to start the first test, to bowl after they missed a two-day warm-up game that ended on Wednesday.
"ECB would like to take this opportunity to thank CSA (Cricket South Africa) for their flexibility on this situation and to emphasise that under normal circumstances we would have wanted to play the match first-class, but illness in the camp has made this very problematic," the ECB said in a statement.
England have had little time to rest after spending seven days at home following a recent two-test series in New Zealand.