Queensland century-maker Peter Forrest overcame illness and South Australia’s bowlers to steer the Bulls to first innings points in the Sheffield Shield match in Adelaide.

Forrest battled a virus sweeping through the Bulls but batted all but nine overs of Friday’s third day of play, as Queensland reached 7-400 at stumps, 13 runs ahead of SA.

Forrest, who made 129, vomited frequently at Glenelg Oval due to a stomach virus crippling the Queenslanders.

The latest victim is Test paceman Ryan Harris, who spent Friday at the team hotel and is unlikely to bowl again in the match.

Bulls coach Stuart Law says no-one knows the origin of the illness, which is affecting players for 48 hours and causing vomiting and diarrhoea.

The virus forced captain James Hopes to be a late withdrawal from the match and has also hit Ben Cutting, Greg Moller, Chris Hartley, Forrest and now Harris.

“Who knows what it is … the doctor here doesn’t know what it is,” Law said.

Forrest was curled up asleep on the dressing room floor after his gallant knock.

“They say mind or matter, and he was just focused on one thing, his batting,” Law said.

“About 3 o’clock this morning he started, it was coming out of both ends – there is no pretty way to say it.

“It was a tough ask but he dug in and did us proud.”

Forrest combined with fellow virus victim Hartley for a defining 194-run partnership for the fifth wicket which ensured the visitors banked first innings points.

Hartley, who left the field after lunch on the Wednesday’s opening day and didn’t return until he came to the crease before lunch on Friday, compiled an invaluable 89.

Both Forrest and Hartley were often on their haunches between balls and spent drinks breaks sitting down with towels draped over the heads.

Given the hardships, Law was rapt to take innings points.

“With the effort we have had to put in, and have basically half a team that is feeling anywhere near decent, it’s monumental effort really,” he said.

Law had a dig at the flat pitch which was proving difficult for batsmen to score freely and for bowlers to take wickets.

“Cricket Australia wanted super-flat wickets,” he said.

“I’m not blaming anyone. But cricket wickets need a bit of grass on them for batters to score runs and for bowlers to take wickets.

“It has been a tough grind.”