Discussions are under way about postponing the match after just five England players - Harry Brook, Zak Crawley, Keaton Jennings, Ollie Pope and Joe Root - turned up for the training at the Pindi Cricket Stadium on Wednesday.

The rest of the squad, including captain Ben Stokes, stayed in the hotel as team officials said six or seven players had been affected by the bug.

Brook, Crawley, Pope and Root have all been named in England's playing XI for the first test due to start on Thursday.

"There's obviously a few guys not feeling 100%," Root told reporters, adding that he didn't feel good on Tuesday but woke up feeling better on Wednesday before training at the stadium.

"It's nothing like food poisoning or COVID … I think it's just one of those things that we've unfortunately picked up as a group. We try to do absolutely everything right to make sure we're prepared really well for this game.

"Sometimes you just pick up a virus and when you're all tied together in one, I tell you, you can spread it out. We did everything we can to try and mitigate that, but you have to see how things go tonight and tomorrow."

England team spokesman Danny Rueben said several England staff members have also been affected.

The Pakistan Cricket Board said it was discussing the start of the test with the England Cricket Board "and will provide further updates in due course."

Root said he wasn't sure whether it was possible to delay the game by a day and have it start on Friday.

"It's such a monumental tour and important series for so many reasons," Root said. "We've waited 17 years to come to Pakistan to play a test match, if it means waiting another day, is that the worst thing in the world?

"We're all desperate to play this game and we know how important it is to the fans of Pakistan and their team as well.

"I don't think it's necessarily the worst thing in the world if we have to wait one more day to make sure the game isn't cancelled and everyone gets what they want, which is an exciting three-match series."