March 2009
Legionnaires' Disease is caused by the Legionella bacteria. It is a very rare form of pneumonia (chest infection). Early symptoms are very similar to influenza. It is diagnosed from a culture of the bacteria from clinical specimens (e.g. sputum) taken from patients thought to be suffering from the infection. The infection can be treated with antibiotics. However, severe cases can result in death.
Legionella bacteria are associated with water and are widespread in the environment. They are found in lakes, rivers, hot springs and other bodies of water as well as soils
Legionella may also be found in cooling towers associated with air-conditioning systems and industrial processes. The temperature of water in these systems is kept between 28°C and 45°C. These conditions allow the bacteria to multiply in large numbers.
Optimal temperatures for Legionella growth are 25°C - 50°C. The most rapid proliferation occurs at 38°C.
Infection is acquired through breathing in aerosols (very fine droplets of water) which contain the bacteria. It is not passed from person to person nor is it acquired by drinking water contaminated with Legionella.
The disease does not affect everyone who comes into contact with the bacteria.
The groups most at risk are:
The Health (Infectious Diseases) Regulations 1990 require cooling towers to be maintained and disinfected in accordance with set Guidelines and Standards (see list below).
Monash University is in compliance with all of the Victorian Government Regulations, Guidelines and Standards (Refer to list below).
Maintenance Services at each Campus of the University carry out regular maintenance checks of Cooling Towers. Cooling towers at most campuses have been or are being fitted with an "Automatic Dosing System". This means that the towers are automatically continuously dosed with a potent Broad Spectrum Biocide (a substance that kills bacteria). On some campuses, cooling towers are additionally dosed with an alternative Biocide by an accredited external contractor. All of these measures are designed to prevent growth of Legionella as well as the emergence of new strains of bacteria.
For all sites, total bacterial counts (TBC) are performed monthly. If the TBCs are elevated immediate further treatment and testing is carried out. An independent (NATA accredited) company carries out the tests. All cooling towers at all campuses are cleaned quarterly. At all campuses testing specific for Legionella is carried out in accordance with the requirements of the Victorian Government Department of Human Services management programmes for cooling towers.
All new cooling towers at the University are fitted with "drift eliminators" and conform to AS/NZS 3666. Drift eliminators decrease the ‘fall out zone" of any aerosols formed by the cooling tower and therefore decrease the possibility of bacterial infection. In addition, all cooling towers at the various campuses are run at relatively low temperatures ranging from 25°C - 34°C.
Contact Occupational Health and Safety on: