Officials say two new cases of porcine epidemic diarrhea have been confirmed through laboratory tests.
One case — a farm in Chatham-Kent — was flagged earlier this week as under investigation after pigs there fell ill.
A spokeswoman for the province's Ministry of Agriculture says the latest case was found at a farm in Norfolk County, which is on the north shore of Lake Erie.
Susan Murray says authorities expect to find more cases since PED is so easy to transmit.
A group representing the province's hog farmers has said the virus is spread through contact with manure, which can cling to trucks, trailers and even clothing and boots.
The country's first case of PED was discovered last week on a farm in southwestern Ontario, and officials say hundreds of piglets between two to five days old have died from the disease.
The virus has also decimated herds in the U.S., and Canadian hog producers have said they worry the same could happen here.
Ontario Premier Kathleen Wynne, who also serves as agriculture minister, is set to discuss a possible national strategy to contain the virus with her federal, provincial and territorial counterparts Thursday.
Ontario Pork has warned the virus could cost the country's pork industry tens of millions of dollars in one year alone if it spreads to other provinces.
Officials stress, however, that there is no risk to human health or food safety.