The Ingenieur Vol 57 January-March 2014 The Ingenieur Vol 57 January-March 2014 | Page 44

INGENIEUR

SPECIAL FEATURE

Control Requirements
for Waterborne
Legionnaire’s Disease
By Ir. Chen Thiam Leong

Both potable and non-potable water supplies harbour Legionella pneumophila,
and have been linked to outbreaks of both hospital- and community-acquired
Legionnaires’ disease. The key prevention is maintenance of the water systems
in which Legionella grow, including drinking water systems, hot tubs, decorative
fountains, and cooling towers.
Legionella acquired its name after a July 1976
outbreak of a then-unknown “mystery disease” that
sickened 221 persons, causing 34 deaths. The
outbreak was first noticed among people attending
a convention of the American Legion - an association
of US military veterans in Philadelphia during
the U.S. Bicentennial year.  On January 18, 1977,
the causative agent was identified as a previously
unknown
bacterium
subsequently
named
Legionella.
Legionnaires’ disease, or Legionellosis, is
a severe infection caused by Legionella species,
primarily L.pneumophila which is responsible for
90% of infections. The disease typically presents as
pneumonia. The incubation period of Legionnaires’
disease is from two to ten days. For several days,
the patient may feel tired and weak. Most patients
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VOL 55 JUNE 2013

who are admitted to the hospital develop a high
fever, often greater than 39.5°C. A cough can be
the first sign of a lung infection. The cough may
be sufficiently severe to cause sputum production
(coughed up mucous). Gastrointestinal stomach
symptoms are common, with diarrhoea being the
most distinctive symptom. Many patients have
nausea, vomiting, and stomach discomfort. Other
common symptoms include headaches, muscle
aches, chest pain, and shortness of breath.
Legionnaires’ disease is not contagious. No
special precautions are necessary. The disease
is transmitted via drinking water, not by infected
persons (hence, it differs from SARS and influenza
where masks must be worn). Likewise, women who
are pregnant and their foetuses have nothing to
fear from patients with the disease.