Victoria has recorded 71 confirmed cases of legionnaires’ disease and one person has died from the disease in an outbreak that authorities say they have narrowed down to two suburbs in Melbourne’s west.
Victoria’s chief health officer, Dr Clare Looker, on Friday confirmed the death of a woman aged in her 90s. She said the woman became ill on Tuesday evening and presented to hospital, where she died shortly after.
“Our condolences are with her family,” Looker said.
“She was an elderly lady who became very suddenly unwell and presented to hospital in very poor health, and passed away that evening.”
On Friday evening, Victoria’s health authorities issued an update saying 71 cases had been confirmed with an additional seven cases suspected in the state’s worst legionnaires’ disease outbreak in more than two decades. The cases were mostly in adults aged over 40 years and all had visited or lived in metropolitan Melbourne.
The outbreak first emerged on 26 July, and as of Friday morning all but one of the confirmed cases and seven of the suspected infections had involved hospitalisation. Several people are in intensive care with severe pneumonia.
Looker said authorities believe people were exposed to the virus between 5 July and 20 July, and presented with symptoms from the 15th.
“Recent weather patterns could explain the wider than usual spread of legionella bacteria with this outbreak,” she said.
“That’s why we’re urging people with symptoms to seek medical advice immediately, especially if you’ve been in metropolitan Melbourne prior to feeling unwell.”
Common symptoms of legionnaires’ include chills, cough, fever, headache and muscle aches and pains. Other atypical symptoms may include nausea, vomiting, diarrhoea and confusion.
Those most at risk are adults aged over 40, people with weakened immune systems, smokers, and those with chronic lung, heart and kidney issues.
Looker said authorities were still looking for a contaminated water source – most likely a cooling tower – that was responsible for the outbreak, and had narrowed the search to Laverton North or Derrimut.
There were 100 cooling towers in the two suburbs – of which 41 had been inspected, tested and disinfected – though she said results would not be available for a number of days.
However, Looker said she was “confident” authorities had already visited the infected tower.
“There’s a high probability that we have already 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. I’m cautious – I obviously can’t say that with certainty until we have test results back.”
The health department has also written to a broader group of 400 cooling tower operators across Melbourne asking them to submit test results.
It is Victoria’s largest outbreak of the infection since 2000, when four people died after Melbourne Aquarium cooling towers became infected with Legionella pneumophila bacteria.
In that outbreak, Looker said it had become “quickly obvious” the aquarium was the common exposure site, which led to widespread testing that included asymptomatic people.
She said this latest outbreak was “unusual” due to the number of symptomatic cases across a broad area.
“We hypothesise there’s a few things that have contributed to that, presumably a reasonably high load of legionella in the cooling tower that has caused this, if that’s what it is, and potentially also the weather patterns,” Looker said.
She said there was evidence that cooling towers with legionella could send aerosols out into the air for “up to several kilometres”.
Experts from the Bureau of Meteorology, as well as air scientists, have been brought in to assist the outbreak response team.
Associate prof Megan Rees, the director of respiratory medicine and sleep disorders at the Royal Melbourne hospital, said though the infection can be severe and some patients may require respiratory support, it can be treated with antibiotics if diagnosed early.
