Police spokesman Mark David said Séraphin, 61, was arrested Apr. 18 after one woman came forward. In the course of the investigation police found a second victim.
"Between 2011 and 2014 he's had sexual relations with two women while he knew that he was HIV-postive," David said.
David said Séraphin appeared in court on Apr. 29 to face a total of seven charges including sexual assault and assault.
Police said Séraphin has been HIV-positive since the 1990s.
"He knew these women, he had long-term relationships with these women, but never disclosed that he had HIV, so this becomes an assault," David said.
David said one of the alleged victims has since been diagnosed with HIV herself.
Police say there could be other victims
David said since Séraphin was diagnosed two decades ago, police believe there may be other victims in the greater Montreal area. He said investigators would like to hear from them.
"It's not necessarily to make a complaint against Mr. Séraphin if they give us a call, but it's to seek medical attention for a possible virus that they might have contracted," David said.
People who have information are asked to contact investigators at 450 463-7211. David said all calls will be kept confidential.