The source of Victoria’s deadly legionnaires’ disease outbreak has been pinpointed, with health authorities confident it has been contained.

A cooling tower at Laverton North in Melbourne’s west has been identified as the source after dozens in the suburb and neighbouring Derrimut were disinfected.

“I am hopeful we’ve contained the source of the outbreak,” Chief Health Officer Clare Looker told reporters on Monday.

“Further work is being undertaken now that we have this positive result to quantify the amount of legionella in the sample.

“Recent weather patterns could explain the wider than usual dispersal of cases.”

A man in his 60s and a woman in her 90s died after being caught in the outbreak.

There are 77 confirmed cases as of Monday. All have been hospitalised.

Legionnaires’ disease is caused by the legionella bacteria, found in natural bodies of water, spas, warm water systems, potting mix and artificial systems that use water for cooling.

Symptoms can include a pneumonia, chest infection, aches, headache, fever, cough and chills.

About 10 per cent of legionnaires’ patients die.

People most at risk are adults aged over 40 years, especially those with other medical conditions, people who are immunocompromised, or those who smoke.