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Legionellosis
is a
life-threatening infectious
disease caused by a bacterium called Legionella. In most of cases it is caused
by Legionella pneumophila. There are approximately 35 Legionella species known
that produce the disease.
The bacteria
are common in natural water sources but they may also be found in urban water
systems where the bacteria can grow under favorable conditions at temperatures
between 25 and 45 °C (77 and 113 °F), e.g. cooling towers or hot water systems.
The bacteria can survive for several months in those wet environments.
People can
get the bacteria by inhaling water or small drops suspended in the air. The
transmission of Legionnaires' disease is not completely understood.
Legionellosis
can have two different forms:
-
Legionnaires' disease, also known as Legion Fever, is the more severe form of
the infection because it affects primarily
the lungs causing pneumonia, a condition in which some of the lungs' air sacs
fill with fluid or pus, so air is excluded. Legionnaires' disease mainly affects
older adults and people with weakened immune systems. If untreated,
Legionnaires' disease can be fatal. First symptoms appear 2 to 14 days after the
exposure
to legionella bacteria.
- Pontiac fever. Only produces a
milder illness resembling acute influenza. Usually, the fever clears on its own
in 2 to 5 days. The first symptoms generally appear a few hours after the
patient has been exposed to the bacterium
Some people
can be infected with the Legionella bacteria and have only mild symptoms or no
illness at all.
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