Clinical DescriptionLegionellosis is associated with two clinically and epidemiologically distinct illnesses: Legionnaires’ disease, which is characterized by fever, myalgia, cough, pneumonia, and Pontiac fever, a milder illness without pneumonia.
Laboratory Criteria For Diagnosis
- Isolation of Legionella from respiratory secretions, lung tissue, pleural fluid, or other normally sterile fluids, OR
- Demonstration of a fourfold or greater rise in the reciprocal immunofluorescence antibody (IFA) titer to greater than or equal to 128 against Legionella pneumophila serogroup 1 between paired acute- and convalescent-phase serum specimens, OR
- Detection of L. pneumophila serogroup 1 in respiratory secretions, lung tissue, or pleural fluid by direct fluorescent antibody testing, OR
- Demonstration of L. pneumophila serogroup 1 antigens in urine by radioimmunoassay or enzyme-linked immunosorbent assay
ConfirmedA clinically compatible case that is laboratory confirmed
CommentsThe previously used category of "probable case," which was based on a single IFA titer, lacks specificity for surveillance and is no longer used.
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. CDC. (1990). Case Definitions for Public Health Surveillance. MMWR, 39(RR-13), 1-43. https://www.cdc.gov/mmwr/preview/mmwrhtml/00025629.htm
3. 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.