Ottawa Public Health is warning that as many as 6,800 people may have come into contact with hepatitis B, hepatitis C or HIV while undergoing an undisclosed procedure at an Ottawa clinic.

The city's chief medical officer, Dr. Isra Levy, announced Saturday that Ottawa Public Health has been probing "an infection control lapse in a local non-hospital medical facility."

In a statement released to the media, Levy said that patients of the clinic will be notified of their potential exposure to disease early next week by registered letter.

The patients who will receive letters will have visited the clinic over a 10-year span dating back from spring of this year.

Jocelyne Turner, spokesperson for the City of Ottawa, said there is no indication that any patients have become infected.

However, it is the agency's duty to notify patients of their potential risk, she said.

"The risk of infection is incredibly low," Turner told in a telephone interview Saturday.

In his statement, Levy said that the risk to the clinic's patients of contracting hepatitis B is less than one in a million, hepatitis C less than one in 50 million, while the risk of contracting HIV is one in three billion.

Ottawa Public Health will not name the doctor, the clinic or the procedure until all patients are notified.

"We don't want to alarm people because the procedure that's involved with this investigation, many other people in Ottawa have undergone this procedure in the 10-year span, so we don't want to cause additional concern," Turner said.

The doctor stopped performing the procedure in June.

The clinic came to the attention of Ottawa Public Health after a routine medical audit found "irregularities" in how it cared for medical equipment, Turner said.

She said Ottawa Public Health can't be sure when those issues began.

Dr. Michael Gardam of Ottawa's University Health Network said warning letters to patients over public health concerns at a clinic are not uncommon, but in each case, the risk to patients is very low.

"This does happen," Gardam told CTV News Channel Saturday evening. "Sometimes it can be a small breach in sterilization practice that goes unnoticed for year after year, and finally when a clinic is being reviewed you can actually see these things and you realize this has been going on and then you send out the letters."

But he cautioned that the viruses in question are "actually quite hard to catch from medical instruments" unless there is a gross breach of sterilization practices.

Ottawa Public Health investigated the clinic for three months, a probe that took so long because the agency chose to review records dating back 10 years.

The investigation was the "most extensive" ever undertaken by the agency, Turner said.

Ottawa Public Health said a call centre will be up-and-running on Tuesday to answer questions from patients and the general public.

Infectious disease specialist Dr. Neil Rau said Saturday's news does not mean the clinic was not sterilizing equipment.

"It doesn't mean they were doing nothing," Rau told CTV News Channel. "There may have been times when they weren't monitoring the process and keeping a log book and doing it properly. But one reassuring thing in the story so far is that they have not said anyone actually has acquired an infection."

According to Rau, the risk of infection is driven by the percentage of the population that has hepatitis B, hepatitis C or HIV.

"Unless this clinic was serving a really indigent population, it's doubtful that the people who are going to that clinic actually have a high chance of having an infection with one of those things," Rau said. "So that already reduces the risk, even if the infection control practices are weak or sub-optimal."