The Holland midfielder had been struggling with sickness in the 48 hours leading up to Saturday’s match, resulting in being ordered by the doctor to stay away from the team hotel the night before the game.
And even though he was still affected during the clash he played a key role, including a brilliant lob over Artur Boruc for Liverpool’s second.
“Thursday night I had a tablet from the doctor for my knee. It was a tablet that could induce stomach pains,” said Wijnaldum, was named man of the match.
“I took it and I had a pain and thought it was from the tablet. In the end I was vomiting and everyone was a little bit scared.
“I didn’t train on Friday and I didn’t sleep at the hotel either because they thought I might infect other players.
“The manager called me and said ‘Do you think you can play?’ I said I was as positive as I can. In the morning I was still weak and had diarrhoea.
“The tablets helped a lot but even at half-time I had to run off to get to the toilet. I was like ‘Oh no!’. I ran inside and I managed to control it!”
However, what was more important was getting back to winning ways after back-to-back 1-1 draws against the Hammers and Leicester had left critics questioning their mettle for a fight.
“We had two draws in a row and that didn’t feel that good,” he added.
“But if we had been told that at the beginning (of the season) you will have this kind of points (65) everyone would have taken it.
“It could be better but we must appreciate where we stand.
“You can see the improvement. You could see at the beginning of the season we improved. We just have to keep it going.”
Liverpool head to Marbella for a warm-weather training break as they are not involved in next weekend’s FA Cup, meaning they return to action in the Champions League at home to Bayern Munich on February 19.
Wijnaldum is optimistic they can realistically fight on two fronts.
“We have to see how it is going to work. I think we can play both,” he said.
“You never know but a lot of times it goes well. Last season the Champions League went well and we dropped a lot of points in the league.
“But I don’t think it was because of the Champions League.”