Second person dies as Legionnaires’ disease cases rise to 77

A second person has died following an outbreak of Legionnaires’ disease in Melbourne’s western suburbs, as contact tracers continue to narrow down the cooling tower believed to be the source of the infections.

There have been 77 confirmed cases of Legionnaires’ disease and another seven suspected cases linked to the outbreak since mid-July. Seventy-five people have been hospitalised.

A man in his 60s started showing symptoms of the illness on July 21 and was admitted to hospital six days later. He died on Thursday.

A woman in her 90s died two days earlier, on Tuesday.

Health authorities have visited and tested 54 of the 100 cooling towers in the Laverton North and Derrimut areas, which have all been disinfected, but it will be days before test results are available.

Victorian Chief Health Officer Dr Clare Looker said she was aware there was concern about the timing of the outbreak and whether it could be linked to a large factory fire in Derrimut on July 10.

More than 180 firefighters battled the blaze at the chemical warehouse, which spewed toxic smoke across nearby homes.

“We have found no evidence from Australia or overseas of Legionella outbreaks being directly caused by large industrial fires,” Looker said.

“We have explored multiple hypotheses with the input of local and international experts in the field, but to date, none of these investigations have revealed a causal link to the recent industrial fire.”

Legionnaires’ disease is a severe form of pneumonia caused by inhaling small water droplets in the air or soil containing the Legionella bacterium. The incubation period is two to 10 days and it is not spread person-to-person.

Looker said a single cooling tower in the Laverton North and Derrimut area was the likely source of the outbreak, as it would be unusual for multiple towers to be affected.

As a result, the Bureau of Meteorology has been called in analyse how weather patterns may have increased the spread past the normal 500-metre radius.

“People would be aware that we’ve had a very cold July,” Looker said.

“The bureau has described quite a strong thermal inversion pattern around the middle of July, and I understand that that could contribute to much broader dispersal of low-lying air...and broader distribution of fine water droplets from a cooling tower.”

Looker said that because the colony of bacteria may have died, the Health Department may never find the definitive source of the outbreak.

In most of the cases, people were exposed to the disease between July 5 and July 20. They developed symptoms on or after July 15.