He was asked about disagreements in the scientific community over the way to handle the pandemic.
It comes after a number of academics signed the so-called "Great Barrington declaration", which says people less vulnerable to coronavirus should be allowed to return to normal life.
The declaration advocates a herd immunity approach while continuing "focused protection" for those most at risk.
Addressing Holyrood's Covid-19 Committee, Professor Leitch said disagreements within the scientific community are nothing new, but those over Covid-19 are taking place more publicly.
In response to a question from the SNP's Shona Robison, he said: "The headline answer is the mainstream scientific advice from around the world is that this virus remains a major threat to global public health and individual lives.
"You will not find a country, a whole country, that has veered from that very much.
"There are nuances, Sweden is often the one quoted to me.
"I said to the chief executive of Swedish healthcare, 'people are telling me you didn't lock down'.
"He said: 'No, no, we locked down, we just have a very compliant population and we didn't have to put it in law.'"
Prof Leitch said scientific disagreement is now playing out "in the public eye".
He added: "I think that's OK, as long as there is balance in the reporting and balance in the messaging and the mainstream public health message is heard.
"I have no difficulty in being held to account for that advice, none at all."
However he said more extreme views, such as saying "face coverings don't work", should be strongly opposed.
He added: "That really, really needs very strong other voices to make sure that that isn't heard by too many people in the country."
Twenty people have died with coronavirus mentioned on the death certificate, which is double the number from last week.
The National Records of Scotland have released the latest Covid statistics showing a marked increase in deaths where the virus was linked.