The Porcine Epidemic Diarrhea virus has now spread to Quebec.
The nasty illness has wiped out millions of piglets in the USA.
It somehow found its way into Ontario where 21 farms have been infected.
This includes three in Perth County, four in Oxford, one case in Middlesex and one in Wellington.
PED has also wormed its way into Manitoba and PEI.
The Canadian Food Inspection Agency is investigating.
It believes the virus may have come in through swine feed.
PED poses no risk to humans or to meat quality.