Prof Emma Thomson says that although large events can cause "super-spreading" of a virus, the Nike conference in Edinburgh at the end of February was "very definitely not the whole story".
That outbreak resulted in 25 cases of coronavirus, including eight in Scotland.
She said that there were "at least 113 introductions" of Covid-19 into Scotland.
"I suspect many people came back, for example from holidays, skiing and things like that with the infection and that took hold in the community on many occasions," she told Radio Scotland.
Prof Thomson has been able to track changes in the virus's genetic code across different regions of Scotland.
She said this enabled scientists to determine which country the infection had come from.
We don't think it's that likely we would have been seeing this virus in Scotland in December. It's certainly possible that it might have been here earlier in February, and a lot less likely that it was here in January based on what we've seen, although we may not have been looking for it at that time.
Prof Emma ThomsonUniversity of Glasgow Centre for Virus Research