The Canadian Food Inspection Agency has confirmed a third commercial flock became infected with highly-pathogenic avian influenza in Ontario.
The third one is in north Waterloo Region, not far from the second case in south Wellington County.
Deaths in a backyard flock in the Bruce Peninsula remain to be confirmed as avian influenza.
The disease is travelling with migrating wildfowl so the Feather Board Command Center has emphasized cleaning boots before entering poultry barns.
The CFIA has established 10-kilometre quarantine zones around the farms infected; the first was a turkey operation at Thamesford, just east of London.
The outbreaks have resulted in export bans on Canadian birds and poultry products.