MEDICAL staff were doing their best to keep a lid on a viral bug that has flattened several members of Queensland's State of Origin squad in camp on the Gold Coast.

Bench forward Jacob Lillyman was the worst affected, confined to his hotel room, while teammate Corey Oates had to quit training and return to his room after being physically ill, vomiting on the sidelines as spectators watched on.

Coach Kevin Walters, however, was playing down fears the whole team could catch the bug, which he said was hopefully just a "24-hour virus".

"There's a couple who've gone down over the last few days and been a bit ill," said Walters after the team completed its second full session at Sanctuary Cove.

"Some the boys have been suffering stomach cramps and have been vomiting but I think we're on top of it now and hopefully they will all be okay to train on Sunday.

"Some were able to train today but not Jacob (Lillyman), he's been hit the worst because of his bigger body so the bug has enjoyed itself and he's been knocked around a fair bit."

Walters said the players would have to keep the fluids up and watch their hygiene.

"I think we're up to about six guys now but I think we will be all right now. It's not a major issue for us, we just have to make sure we stay on top of it.

"But that's Origin isn't it? It's smooth sailing and all of a sudden you hit some rough water."

Walters has enough problems with young Newcastle flyer Dane Gagai, who scored the only try for Queensland in its 6-4 win in game one in Sydney, still causing some concern with a quad strain.

Reports on Gagai's progress were mixed but Walters was putting a positive spin on his chances of playing on Wednesday night.

"He's looking good. He didn't train again with the main squad but we'll give him a good test out on Sunday and see how he goes," he said.

Gagai did some solo sprints and looked to be at about 80% capacity.

He had his quad strapped tightly but did not look in any discomfort, although the real test will come tomorrow when he will have to show some explosiveness and take some contact on the injury.

If he gets through the session and pulls up well the following morning he will play, otherwise North Queensland's grand final hero Kyle Feldt will be handed his State of Origin debut.

Queensland will train again tomorrow morning and then have a full throttle training run on Sunday.