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Legionella
pneumonia is clearly underdiagnosed due to several factors
that we will discuss below. This is reflected in the incidence variation found
in the different scientific studies, as well as in the percentage of its etiological
participation in community-acquired pneumonia: it is estimated that
something around 0.5% and 10% of the community-acquired pneumonia
requiring hospitalization is caused by
Legionella
.
1
Besides, the prevalence
and incidence vary according to the region. In order to try to change this
scenario and increment the diagnosis, it is fundamental the knowledge of
its entire infectious chain and diagnostic methods.
Many relate it to the “air conditioning infection”. The origin of the term,
probably, dates back to its discovery when an epidemic occurred in a hotel
in Philadelphia. At the time, in 1976, the outbreak attacked the military
veterans reunited to a convention that included the celebrations for the
bicentennial of the independence of the USA. The bacterium, eliminated
by the air conditioning system in the rooms, was inhaled by the American
legionnaires, hence the name “Legionnaires’ disease”, and, afterwards,
Legionella
sp bacterium. Despite the incrimination of the air conditioning,
a range of other sources of infection emerged in the subsequent studies and
nowadays they assist the doctors in the investigation of the infection.
Legionella
is found out in the aquatic environment, where it survives and
proliferates in large amounts at the ideal temperature of 20 °C to 42 °C. In
this environment it finds a great ally: amoebae.
Legionella
can multiply and
even survive at the interior of amoebae. We find the bacterium in streams,
lakes, estuaries and coastlines. Moreover, the bacterium can survive in the
pipes of human buildings, housing in the biofilms. Old pipes with stagnated
water areas retain the
Legionella
which is then released by the water flow
and pressure. The suspended and inhaled water in the form of aerosols
