https://www.cbc.ca/news/politics/cbs...irus-1.5498866
It looks like Canadian citizens, permanent residents, and (for now) US Citizens are exempt, though they are requiring health checks for all inbound travelers.
Canada is barring entry to all travellers who are not Canadian citizens or permanent residents, Prime Minister Justin Trudeau announced today — one of a set of extraordinary new measures being introduced to stop the spread of COVID-19.
There will be exceptions for air crew, diplomats, immediate family members of citizens and, "at this time," U.S. citizens, Trudeau said.