Legionnaires’ source mystery as city cases keep rising

The number of people with legionnaires’ disease has risen again in 24 hours, but the origin remains a mystery as health authorities continue their investigation.

There are 40 patients suffering from the disease, most of whom have been hospitalized with some admission to intensive care because of severe cases of pneumonia, Victoria’s Department of Health says.

Test results for another six people suspected of having the disease are due back soon.

Most of the patients are over 40 years old and all have visited or live in metropolitan Melbourne.

The health authority is testing potential sources across the city and Victorian chief health officer Clare Looker said she believed the origin was a single cooling tower.

“These numbers that we’re seeing at the moment are much greater than the usual three to six that we see a week so we think most cases are from a single source,” Dr Looker told reporters on Tuesday.

Eighteen cooling towers at public venues, factories and industrial sites have been disinfected but the source has yet to be confirmed.

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

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

People with underlying diseases, particularly those who are immunocompromised, elderly people and smokers are at greater risk of infection.