A Covid patient in the ICU in a hospital outside Paris, France
Representational image AFP / ALAIN JOCARD

Victoria on Friday recorded the first death caused by Legionnaires' disease, as health authorities claimed they have narrowed down the source of the outbreak to two suburbs in Melbourne's industrial west.

On Friday, Chief health officer Dr Clare Looker confirmed the death of the woman in her 90s, who was hospitalized on Tuesday. By Friday afternoon, there were 71 confirmed and more suspected cases, with several of them in intensive care, The Guardian reported.

Victorian authorities have narrowed down their investigation into the source of infection in Laverton North or Derrimut. Of the 100 cooling towers in the area, authorities have checked and disinfected 41.

Looker said the authorities may have disinfected the contaminated tower.

"There's a high probability that we have already visited the tower and disinfected it," she said. "That is really driven by some pretty compelling epidemiology and crossover of where many of our cases have visited. I'm cautious – I obviously can't say that with certainty until we have test results back."

The authorities have also asked 400 cooling towers in Melbourne to submit their test results.

Looker said the outbreak this year was "unusual," as there were more symptomatic cases. While the disease was not spread by person-to-person contact, the cases may rise in the latest outbreak due to the incubation period, reported ABC News.

Authorities were also checking the transmission of Legionnaires' disease through weather, as most patients infected have been living in Melbourne's west. According to Looker, the cold July weather may have contributed to the outbreak.

Experts from the Bureau of Meteorology and air scientists have been assisting the outbreak response team.