National case definition: Legionnaires' disease and Pontiac fever (Legionellosis)
Date of last revision/review: May 2008
Only confirmed cases of disease should be notified.
Type of surveillance
Routine case-by-case notification to the federal level.
- Clinical illness (see Clinical evidence section) with laboratory confirmation of infection:
- isolation of Legionella species or detection of the antigen from respiratory secretions, lung tissue, pleural fluid or other normally sterile fluids
- a significant (e.g. fourfold or greater) rise in Legionella species IgG titre between acute and convalescent sera
- IgG titre > 1:128 against Legionella species
- demonstration of L. pneumophila antigen in urine (see Laboratory comments section)
Clinical illness with demonstration of Legionella species DNA
Jurisdictions should use a validated antigen detection test, and test interpretation must be in accordance with the manufacturer's instructions. The urinary antigen test (UAT) is widely used in Canada and internationally. UAT targets Legionella pneumophila serogroup 1 but is not validated to target other serogroups or species in the genus.
Few laboratories use culture with biochemical confirmation in conjunction with antigen detection. A limited number of laboratories currently participate in College of American Pathologists (CAP) and Clinical Microbiology Proficiency Testing (CMPT) proficiency testing programs.
Legionellosis comprises two distinct illnesses: Legionnaires' disease, characterized by fever, myalgia, cough and pneumonia, and Pontiac fever, a milder illness without pneumonia.
- A48.1 Legionnaire's Disease
- A48.2 Pontiac Fever
- 482.8 Legionnaire's Disease
Type of international reporting
Under Article 6 of the International Health Regulations (IHR) (2005), each State Party shall notify the World Health Organization (WHO) by way of the IHR National Focal Point, and within 24 hours of assessment of public health information, of all events which may constitute a public health emergency of international concern within its territory in accordance with the decision instrument (Annex 2 of the IHR), as well as any health measure implemented in response to those events.
- Any event of potential international public health concern, including those of unknown causes or sources, shall lead to the utilization of the algorithm in Annex 2 of the IHR. The need to notify such events to the WHO will depend upon the outcome of the assessment using the Annex 2 decision instrument. Note: If event does not meet the criteria for notification under Article 6 of the IHR, then other IHR-related reporting requirements may still apply with WHO and/or other States Parties, including those under Art. 7 (information-sharing during unexpected or unusual public health events), Art. 8 (consultation with WHO on public health events), Art. 9 (any public health risk that may cause international disease spread), Art. 10 (requests for verification from WHO), and Art. 44 (collaboration and assistance).
Probable case definitions are provided as guidelines to assist with case finding and public health management, and are not for national notification purposes.
World Health Organization. International Health Regulations (2005). 3rd ed. Geneva, 2016, from http://www.who.int/ihr/publications/9789241580496/en/
Previous case definitions
Canadian Communicable Disease Surveillance System: disease-specific case definitions and surveillance methods. Can Dis Wkly Rep 1991;17(S3).
Case definitions for diseases under national surveillance. CCDR 2000;26(S3).
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