The patients would have undergone echo-endoscopies at l'Hotel-Dieu hospital in Levis, Que., or at the Alphonse-Desjardins medical centre.
Authorities announced Monday that certain devices used in probes of the digestive system might not have been properly sterilized.
They said the actual risk of transmission during the procedure was quite low.
But they said they had confirmed the identity of all patients who underwent the procedure since 2005. Seventy per cent of them are from the Quebec City region, and 30 per cent are from outside that area.
The people in question will receive letters, starting next week, with instructions on steps to take. A 1-800 telephone hotline will also be set up.
"Even if the risk is nearly non-existent we have decided to offer screening for Hepatitis B and C, and for HIV," said Dr. Andre Vincent, head of the department of labs at Alphonse-Desjardins.
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