LEGIONNAIRES' DISEASE
(Legionella spp.)

Clinical Criteria
Any person with pneumonia

Laboratory Criteria
- Laboratory criteria for case confirmation
At least one of the following three:
– Isolation of Legionella spp. from respiratory secretions or any normally sterile site
– Detection of Legionella pneumophila antigen in urine
– Legionella pneumophila serogroup 1 specific antibody response

- Laboratory criteria for a probable case
At least one of the following four:
– Detection of Legionella pneumophila antigen in respiratory secretions or lung
tissue e.g. by DFA staining using monoclonal-antibody derived reagents
– Detection of Legionella spp. nucleic acid in a clinical specimen
– Legionella pneumophila non-serogroup 1 or other Legionella spp. specific
antibody response
– L. pneumophila serogroup 1, other serogroups or other Legionella species: single
high titre in specific serum antibody

Epidemiological Criteria
At least one of the following two epidemiological links:
– Environmental exposure
– Exposure to the same common source

Case Classification
A. Possible case   NA
B. Probable case
Any person meeting the clinical criteria AND at least one positive laboratory test for a
probable case OR an epidemiological link
C. Confirmed case
Any person meeting the clinical and the laboratory criteria for case confirmation