Ottawa Public Health says the letters will be going out to people who had procedures at a local medical facility, the Canadian Broadcasting Corp. reported.
Provincial health official Isra Levy said Saturday he did not know of any of 6,800 patients having become ill with Hepatitis B, Hepatitis C or HIV and said the risk of infection was "very low."
The name of the non-hospital medical facility where the "lapses of infection control" occurred was not revealed, the CBC said.
"We don't know how long the problem has been going on for," Levy said. "We were notified at public health earlier in the summer."