Poulter backed up an opening-round 65 with 3-under 68 to lead over Aussie Mathew Giles.
'I didn't feel too good when I woke up this morning, I wasn't good at all. Must have had something bad to eat last night, unfortunately. So I felt a bit weak out there today,' Poulter said. 'It showed, I hit it terrible, got myself out of position a number of times, but my short game was on and I holed a few nice putts. So, I would've taken that score.'
Geoff Ogilvy recovered from bending his putter in anger on Thursday to shoot 5-under 66 and trail by four shots.
Poulter secured his lead with closing birdies on the final par-5 holes. As much as the illness affected Poulter physically, he hopes to overcome the bug to focus on what he says is a tricky course.
'It would be nice to go out there having my mind on the golf game rather than other things,' he said. 'This golf course is very challenging, there's a number of tricky tee shots and secondshots. You can get caught out at any time.'