Gray said the rising number of cases was a “worry” and expected them to increase further in the next few weeks.
“It is impossible to tell for certain because it depends on how the flu spreads, but at the moment it appears to be following the same trajectory as we saw last year which saw a short and sharp, sudden spike,” he told BBC Scotland’s The Sunday Show.
“That is happening earlier this year, which is part of the issue we are facing, but we can expect the continued trajectory to rise over the coming weeks.”
Currently Glasgow and the west of the country is facing the highest rates, along with the Grampian health board area, but he expected that to spread throughout Scotland.
Gray said about 1.5 million people eligible for a free vaccine had taken up the offer since the 2025 rollout began.
He told the programme uptake had been higher this year than in previous years, particularly among adults.
