The England and Wales Cricket Board has informed the Pakistan Cricket Board that they are in a position to field an XI, and the match will get underway on Thursday at the Rawalpindi Cricket Stadium.
However, England have not announced whether they will be fielding the same team as the one they announced on Wednesday.
Approximately 13 to 14 members of the travelling group were affected by a viral infection with around half of that number members of the playing squad, the PA news agency understands.
England had tried to mitigate the risk of issues in Pakistan and made additional preparations including hiring their own chef for the tour for the first time, but a number of the squad were still struck down and remained at the hotel instead of taking part in the final optional training session on Wednesday morning.
The decision was delayed to allow sufficient players to recover in time, after all those affected were confined to isolation in their rooms to prevent the sickness spreading further and allow those feeling unwell to recover, with captain Ben Stokes among those affected.
Mark Wood missed training on Tuesday through illness with other members reporting symptoms later on in the day and although Root said he had experienced symptoms on Tuesday, he has since recovered and took part in training on Wednesday morning.
The session was made optional before the sickness struck but head coach Brendon McCullum was on hand to put Harry Brook, Zak Crawley, Keaton Jennings, Ollie Pope and Root through their paces in the nets.
Stokes had named his nominal starting XI for the match, including handing a debut to Liam Livingstone and a first Test recall since 2016 for Ben Duckett, but his plans could be forced to change due to the illness.
Pakistan will field four debutants in the match, with Saud Shakeel, Haris Rauf, Mohammad Ali and Zahid Mehmood all named.