The Canadian Air Force (CAF) learned about the infection when the aircraft was already in the air.
In order to avoid the possible spread of the infection, it was decided return the aircraft to Canada instead of continuing its flight to Latvia, the representative of the Canadian Joint Operations Command (CJOC) said in an email.
About 70 soldiers and crew members were aboard the plane.
The soldiers will have to be re-quarantined for two weeks before being sent to Latvia.
Canada commands the international NATO fighting group, and there are currently 540 Canadian soldiers in Latvia.
In July, the replacement of Canadian soldiers deployed in Latvia is scheduled to be rotated. The plane should have returned 70 soldiers whose mission in Latvia is over to Canada.
Now the Canadian Army is considering other options for transporting them home.