Somerset bowlers Dominic Bess and Craig Overton have been called up by England for their tour of South Africa after the camp was hit by illness.
Several members of England's touring party are ill with flu-like symptoms, less than a week before the start of the first Test on Boxing Day.
As a consequence, Friday's warm-up against South Africa A has been downgraded from its first-class status.
Stuart Broad, Jofra Archer and Jack Leach have not travelled to the game.
Off-spinner Bess and seamer Overton are due to arrive in Johannesburg on Saturday.
England will play four Tests, three one-day internationals and three Twenty20 matches during this tour, before moving on to Sri Lanka in March.