Purim celebrations were cancelled at the synagogue on Monday as a result, and the building did not reopen on Tuesday.
Other Toronto faith-based organisations have recently cancelled their special events and general operations “out of an abundance of caution,, the shul said.
Canadian broadcaster CTV said the man had attended last week’s Aipac conference in Washington.
Several other people have been taken ill after attending the event organised by the US Israel lobby group.
The Ministry of Health in Ontario, the province that includes Toronto, said there were 34 cases of the coronavirus in the province as of Monday morning.