India captain Rahul Dravid told reporters at Stormont that wicket-keeper batsman Mahendra Singh Dhoni, the first to fall ill, fast bowler Shathakumaran Sreesanth, medium-pacer Agit Agarkar, off-spinner Ramesh Powar and left-arm quick Rudra Pratap Singh were all suffering from viral fever and 'flu.
Dravid added he too was feeling unwell as were batsman Yuvraj Singh, and left-arm pace bowler Zaheer Khan.
"Quite a few boys in our team are suffering from viral fever and 'flu," and symptoms of that kind," Dravid explained. "Sreesanth, Agit Agarkar, Dhoni, RP Singh and Ramesh Powar have not come to practice today (Monday).
"There are other guys like Yuvraj Singh, myself, Zaheer Khan and Robin (Singh, the fielding coach) who are feeling a bit down."
Uncapped 28-year-old Baroda pace bowler Rakesh Patel, who has been playing club cricket in Liverpool, north-west England, has been called up to India's one-day squad.
"In consultation with the board and the chairman of selectors we have called up Rakesh Patel from one of the leagues here as back-up for the fast bowlers because with Sreesanth and Agit unlkely to play tomorrow (Tuesday), Zaheer a bit doubftul, we were a bit light in that department," Dravid said.
Meanwhile 18-year-old quick Ishant Sharma, who has played one Test, and uncapped seamer Ranadeb Bose, both due to join the Test squad later this tour, have been drafted in with a view to being available for the second of three one-day internationals against South Africa at Stormont on Friday.
London-based Nitin Patel will provide cover for injured India physiotherapist John Gloster who tripped over a boundary rope at Stormont on Friday and broke his hand.
India and South Africa are set to complete their series on Sunday.
After that series, India play arch-rivals Pakistan in a one-day international in Glasgow on July 3.
They then face England in three Tests and seven one-dayers from July 19-September 8.
India opened their tour with a nine wicket win in a one-day international against Ireland at Stormont on Saturday.