A Legionnaire’s disease outbreak in Quebec City has killed 10 people since late July, health authorities in the Canadian city say.

A total of 165 people have so far been diagnosed with the disease, which poses a risk for people with weak immune systems, but can be treated with antibiotics.

The regional health authorities, who issued an updated toll on Saturday, said the most recent count includes cases reported over the past 10 to 15 days, as Legionnaire’s has an incubation period of two to 10 days.

Health authorities have launched an investigation to determine the cause of the outbreak.

They suspect improper maintenance of cooling units in air-conditioning systems are at fault for the outbreak.

Legionella bacteria grow in stagnant water in such appliances, then spread with droplets expelled by the system during operation.

Legionnaire’s disease – discovered in 1976 during a veterans convention in the United States, where 29 people died – causes high fever, dry cough and pneumonia.