Legionnaires’
disease is an uncommon form of pneumonia. The disease has
no particular clinical features that clearly distinguish it
from other types of pneumonia, and laboratory investigations
must therefore be carried out in order to obtain a diagnosis.
The following definitions have been agreed for the European
surveillance scheme: |
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Confirmed
case |
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An
acute lower respiratory infection with focal signs of pneumonia
on clinical examination and/or radiological evidence of pneumonia
and one or more of the following: |
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Isolation
of any Legionella organism from respiratory secretion,
lung tissue or blood.
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A
fourfold or greater rise in specific serum antibody titre
to L. pneumophila sg1.
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The
detection of specific Legionella antigen in urine using
validated reagents and methods recommended by EWGLI in
1998.
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Presumptive
case |
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An
acute lower respiratory infection with focal signs of pneumonia
on clinical examination and/or radiological evidence of pneumonia
and one or more of the following: |
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A
fourfold or greater rise in specific serum antibody titre
to L. pneumophila other serogroups or other Legionella
species.
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A
single high titre* in specific serum antibody to L. pneumophila
sg1 or other serogroups or other Legionella species.
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The
detection of specific Legionella antigen in respiratory
secretion or direct fluorescent antibody (DFA) staining
of the organism in respiratory secretion or lung tissue
using evaluated monoclonal reagents.
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The
detection of Legionella specific DNA by polymerase chain
reaction (PCR).
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*A
single high serological titre: as differing serological
testing methods are used in different countries, and as an
internationally accepted validation exercise has not been
carried out, no specific serological test or titre level can
be specified. It is suggested however that the single high
titre result considered to indicate recent Legionella infection,
in the presence of compatible symptoms, be set at a sufficiently
high level to be specific for Legionella infection (i.e. to
produce a low level of false positives). |
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