09/14/2012 11:17 EDT | Updated 11/14/2012 05:12 EST

New legionnaires' cases in Quebec City raise total to 180

Three more cases of legionnaires' disease have been reported in Quebec City, bringing the total confirmed cases to 180 in the outbreak that has killed 13 people.

Health officials say the situation is under control, despite the most recent death reported just Thursday from the acute, sometimes fatal respiratory disease caused by the Legionella bacterium.

Regional health director Dr. François Desbiens, says one of the recent cases showed symptoms on Sept. 4, meaning the person likely contracted the disease while decontamination efforts were still underway.

Officials believe the Legionella that causes legionnaires' was breeding in stagnant water in a cooling before spreading in the mist it released.

The city has since taken measure to ensure cooling towers in the outbreak zone have been cleaned and disinfected.

"It is inside our period of major intervention, so we think that it does not invalidate our conclusion that one of the cooling towers was responsible for what we've seen in the region and that this case has been in contact with the air that was contaminated during that time," Desbiens said Friday of the most recent case.

The outbreak started in the city's lower town.

Officials expected that more cases could present after the potential source was identified and cleaned because symptoms often don't present for more than two weeks.

Despite the latest case, Desbiens says he's still optimistic the massive decontamination effort was successful.