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Legionellosis / Legionnaires' Disease or Pontiac Fever
2005 Case Definition

Legionellosis / Legionnaires' Disease or Pontiac Fever
2005 Case Definition
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NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

CSTE Position Statement(s)

  • 05-ID-01
  • 09-ID-45

Clinical Description

Legionellosis is associated with two clinically and epidemiologically distinct illnesses: Legionnaires’ disease, which is characterized by fever, myalgia, cough, and clinical or radiographic pneumonia; and Pontiac fever, a milder illness without pneumonia.

Laboratory Criteria For Diagnosis

Suspected:

  • By seroconversion: fourfold or greater rise in antibody titer to specific species or serogroups of Legionella other than L. pneumophila serogroup 1 (e.g., L. micdadei, L. pneumophila serogroup 6).
  • By seroconversion: fourfold or greater rise in antibody titer to multiple species of Legionella using pooled antigen and validated reagents.
  • By the detection of specific Legionella antigen or staining of the organism in respiratory secretions, lung tissue, or pleural fluid by direct fluorescent antibody (DFA) staining, Immunohistochemistry (IHC), or other similar method, using validated reagents.
  • By detection of Legionella species by a validated nucleic acid assay.

Confirmed:

  • By culture: isolation of any Legionella organism from respiratory secretions, lung tissue, pleural fluid, or other normally sterile fluid.
  • By detection of Legionella pneumophila serogroup 1 antigen in urine using validated reagents.
  • By seroconversion: fourfold or greater rise in specific serum antibody titer to Legionella pneumophila serogroup 1 using validated reagents.

Case Classification

Suspected

A clinically compatible case that meets at least one of the presumptive (suspected) laboratory criteria.

  • Travel-associated: a case that has a history of spending at least one night away from home, either in the same country of residence or abroad, in the ten days before onset of illness.

Confirmed

A clinically compatible case that meets at least one of the confirmatory laboratory criteria.

  • Travel-associated: a case that has a history of spending at least one night away from home, either in the same country of residence or abroad, in the ten days before onset of illness.

Comments

The 2005 case definition appearing on this page was first published in the 2005 Council of State and Territorial Epidemiologists (CSTE) position statement 05-ID-011 and then re-published in the 2009 CSTE position statement 09-ID-452. The case definitions in the 2005 and 2009 CSTE position statements are identical.

References

  1. CSTE. Strengthening surveillance for travel-associated legionellosis and revised case definitions for legionellosis. Position statement 05-ID-01 available at http://www.cste.org/resource/resmgr/PS/05-ID-01FINAL.pdf.
  2. CSTE. Public health reporting and national notification for legionellosis. Position statement 09-ID-45 available at http://www.cste.org/resource/resmgr/PS/09-ID-45.pdf.

Related Case Definition(s)

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Last Reviewed: April 16, 2021
Source: Office of Public Health Data, Surveillance, and Technology