Woman dies as contact tracers identify suspected source of Legionnaires’ outbreak

Contact tracers suspect a cooling tower in Melbourne’s west is the unusual source of a deadly outbreak of Legionnaires’ disease that has killed one woman and grown to 70 confirmed and suspected cases.

A woman in her 90s died on Tuesday after contracting the disease, which Victorian Chief Health Officer Dr Clare Looker said was spreading through the Laverton North and Derrimut areas of Melbourne.

The elderly woman was admitted to hospital after becoming seriously ill on Tuesday and died a short time later.

“Our condolences are with her family,” Looker said.

“We’re urging people with symptoms to seek medical advice immediately,” she said, adding that a cough and fever were the most common signs of an infection.

Looker said 59 people had been hospitalised as a result of the latest outbreak, which has involved 60 confirmed and 10 suspected cases. Several Victorians have been placed in intensive care.

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

Health authorities have visited 41 of the 100 cooling towers in the Laverton North and Derrimut areas, which have all been disinfected following the outbreak. They will visit another 15 sites on Friday.

Contact tracers homed in on Derrimut and Laverton North after speaking to patients about their movements over the past 10 days. These movements were then plugged into specialised mapping software that identified common exposure sites.

Unusually, these common exposure sites were not shopping centres bustling with people but large, open industrial areas.

“It is unexpected when we get it in industrial areas ... they’re not typically places where lots of the public will go,” Looker said. “This is an unusual outbreak we are dealing with. We’re trying to keep our investigation as broad as possible.”

While authorities suspect one industrial cooling tower is responsible for the latest outbreak, they are awaiting test results, which could take up to 10 days, to identify its precise location.

“I think there’s a high probability that we have visited the tower and disinfected it,” Looker said.

“That is really driven by some pretty compelling epidemiology and crossover of where many of our cases have visited.”

It is the state’s most significant outbreak of Legionnaires’ disease since a 2000 outbreak at Melbourne Aquarium that led to 150 people falling ill and four deaths.

Authorities believe Melbourne’s cold weather has fuelled the spread of the disease beyond the 500-metre radius normally expected.

“We had a very cold … middle [of] July,” Looker said. “There were certain patterns of thermal inversion that can cause air to spread at much further distances and at a lower level.”

Air scientists are looking at whether wind patterns also contributed to the disease’s large geographical spread, which could span several kilometres from the contaminated cooling tower.

The incubation period for Legionnaires’ disease is two to 10 days. It is not spread from person-to-person, but by inhaling small water droplets in the air or soil containing the Legionella bacterium .

People over 40, smokers and those with weakened immune systems are particularly vulnerable to the disease.

Royal Melbourne Hospital associate professor Megan Rees said while the most common symptoms of Legionnaires’ disease were a cough and fever, it could also cause muscle aches, confusion and in rare cases, kidney impairment.

People can also be asymptomatic, she said. The disease is detected through a urine test and treated with antibiotics. Some very unwell patients will wind up in intensive care units and need to be put on dialysis.

“Some people are unwell for a long period of time and need more extensive support,” Rees said.

About three of four cases of Legionnaires’ disease are normally detected in Victoria every week.

Premier Jacinta Allen urged Victorians to seek urgent medical attention if they were experiencing any symptoms associated with Legionnaires’ disease.

“This is a really terrible illness and can cause death,” she said, expressing her condolences for the family of the woman in her 90s who had died.

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