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:
Clinical criteria: Any person with pneumonia
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
- Possible case
NA
- Probable case
Any person meeting the clinical criteria AND at least one positive laboratory test for a probable case OR an epidemiological link
- Confirmed case
Any person meeting the clinical and the laboratory criteria for case confirmation
The above definitions are taken from the Commission Decision of 28 April 2008 amending Decision 2002/253/EC laying down case definitions for reporting communicable diseases to the Community network under Decision No 2119/98/EC of the European Parliament and of the Council