Dr George Christos

covid19 & other Infectious diseases

Legionnaires Disease outbreak in Sydney CBD

There has been a legionnaires disease outbreak in Sydney CBD. The details of the outbreak are in the news report attached. I am more interested to know how it spread and what exactly it is.


Legionnaires’ disease is a form of atypical pneumonia caused by any species of Legionella bacteria, quite often Legionella pneumophila. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. Nausea, vomiting, and diarrhea may also occur.

The incubation period for Legionnaires’ disease ranges from 2-10 days, but is usually 5-6 six days.

Legionnaires’ disease doesn’t spread from person to person. Instead, the bacteria spreads through mist, such as from air-conditioning units for large buildings. Adults over the age of 50 and people with weak immune systems, chronic lung disease or heavy tobacco use are most at risk.

Many people exposed to the bacteria don’t develop symptoms. Those who do develop symptoms may experience cough, fever, chills, shortness of breath, muscle aches, headaches and diarrhoea.

Legionnaire’s disease can be treated with antibiotics.

The only people who are risk are the ones who live or work around large towers of water on top of rooftops for air-conditioners. 5 people have it in the age range 40-70. Authorities are warning people who have been in the area in the last 10 days. I should have noted that air-conditioners are the main means of spread.

The death rate is from 5-10%, normally around the lower end, but immuno-compromised people are are greatest risk 40-80%, but with proper early intervention this can be brought down to 10-30%.

Since it doesn’t spread from person to person there is nothing to worry about, unless it starts to develop of all the water towers in the cities.

An outbreak of this disease in Philadelphia in 1976, largely among people attending a state convention of the American Legion, led to the name “Legionnaires’ disease.” Subsequently, the bacterium causing the illness was named Legionella pneumophila and the name of the illness was changed to Legionellosis.

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