The Ingenieur Vol 57 January-March 2014 The Ingenieur Vol 57 January-March 2014 | Seite 45

SOURCE OF THE LEGIONELLA PATHOGEN
Legionnaires’ disease is a global public health
issue. According to CDC’s Morbidity and Mortality
Weekly Report (August 2011), Legionnaires’
disease increased 217% between 2000 and
2009. The disease-causing bacterium, Legionella
pneumophila, is a waterborne pathogen found in
natural and man-made water systems.
Legionella are natural inhabitants of water
and can be detected in rivers, lakes and streams.
One type of Legionella species (L. longbeachae)
has been found in potting soil. The major source
is water distribution systems of large buildings,
including hotels and hospitals. Cooling towers
have long been thought to be a major source
for Legionella, although some new data suggest
that this may be an overemphasised mode
of transmission. Other sources include mist
machines, humidifiers, whirlpool spas, and hot
springs. Both potable and non-potable water
supplies harbour Legionella pneumophila, and
have been linked to outbreaks of both hospitaland community-acquired Legionnaires’ disease.
More specifically, Legionella bacteria are found
in the environment, usually in warm water. They are
not transmitted from person to person. People
get Legionnaires’ disease or Pontiac fever when
they breathe in a mist or vapour (small droplets of
water in the air) that has been contaminated with
Legionella bacteria. Keeping Legionella bacteria out
of water is key to preventing infection. Most people
with Legionnaires’ disease have pneumonia (lung
infection) since the Legionella bacteria grow and
thrive in the lungs.
PREVENTION
The key to preventing Legionellosis is maintenance
of the water systems in which Legionella grow,
including drinking water systems, hot tubs,
decorative fountains, and cooling towers. Guidelines
for appropriate water temperatures and chem