Legionella infections (Legionnaire’s disease) are notifiable diseases in all jurisdictions in Australia. A notifiable disease requires the mandatory reporting of clinically diagnosed cases of disease to regulatory authorities within 24 hours of confirmed diagnosis. Here in Australia reports average 1.5 – 2.0 cases per 100,000 population year. These figures are consistent with other countries with similar Legionella control regulations internationally. At least 50% of these cases are attributable to sporadic cases of disease, such as those associated with health care facilities.



An average of 49 cases of Legionnaire’s disease were reported in South Australia over the last 5 years. Of these, roughly 50% of the cases were associated with building water systems rather than other sources, such as cooling towers or potting mixes.

Global Picture

Recent European data suggests that healthcare facilities account for between 15% and 20% of annual cases of Legionnaire’s disease. This would equate to as much as 90 cases of disease per annum in Australia. Advances in treatment of the disease have meant that the fatality rate has dropped from between 20% and 25% of cases to between 10% and 15% of cases. However, fatalities associated with healthcare premises can be as high as 40% due to the health status of those infected. This would equate to 30+ fatal cases of disease in healthcare facilities annually.

Global estimates are that approximately 65% of health care facilities have detectable Legionella contamination. Previously detecting Legionella bacteria in a system makes the facility significantly more likely to experience cases of disease. In the majority of cases where Legionella bacteria are present in a healthcare facility, the contamination is systemic. This means that the bacteria are present throughout the system.

Explaining the Legionnaire’s Disease Trend

As the chart above demonstrates, there has been a continuing upward trend in notifications over the past two decades. The reasons for this increasing trend are in part due to better diagnostic techniques. This is due to the increasing aged population and persons with compromised immune systems. It is also likely that notified cases of disease are an underestimate and that the upward trend is likely to continue. However, global opinion is that Legionnaire’s disease from building water system are preventable. So it requires a concerted effort on the part of the facility operators and maintenance staff to focus on water treatment and management.