Related Experiment Video
Updated: Mar 31, 2026
Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
Published on: February 22, 2017
1974 outbreak of Legionnaires' Disease diagnosed in 1977. Clinical and epidemiological features
Abstract:
An illness characterized by high fever and pneumonia struck 2.9% of a group of the Independent Order of Odd Fellows attending a convention held in Philadelphia, in September, 1974. The convention headquarters was the hotel where the American Legion met in July, 1976. The epidemiological, clinical, and laboratory characteristics of the illness were nearly identical to those of the disease in American legionnaires in 1976. Illness was significantly associated with attendance at one convention activity held on Monday morning, Sept. 16, 1974, in the grand ballroom of the hotel. A serological survey in February and March, 1977, showed that people who had attended the convention and became ill were more likely to have raised indirect fluorescent antibody titres than persons who had attended and remained well. The illness seen in Odd Fellows members in September, 1974, was caused by the legionnaire's disease organism.
Insights
Legionnaires' disease caused a pneumonia outbreak among Independent Order of Odd Fellows members in 1974. This outbreak shared characteristics with the 1976 American Legionnaires disease event.
Area of Science:
- Epidemiology
- Infectious Diseases
- Microbiology
Background:
- A mysterious illness causing high fever and pneumonia affected attendees of a 1974 convention in Philadelphia.
- The illness's characteristics closely resembled those of Legionnaires' disease identified in 1976.
Purpose of the Study:
- To identify the cause of the 1974 outbreak among Independent Order of Odd Fellows members.
- To investigate the association between the illness and specific convention activities.
- To confirm the etiological agent through serological testing.
Main Methods:
- Epidemiological investigation of the outbreak, including case finding and exposure assessment.
- Clinical and laboratory analysis of affected individuals.
- Serological survey using indirect fluorescent antibody testing to assess immune response.
Main Results:
- 2.9% of convention attendees contracted the illness, exhibiting symptoms of high fever and pneumonia.
- Illness was strongly linked to participation in a specific activity held in the hotel's grand ballroom.
- Serological data indicated higher antibody titers in ill attendees compared to well attendees, supporting a common exposure.
Conclusions:
- The 1974 outbreak among Independent Order of Odd Fellows members was identified as Legionnaires' disease.
- The legionnaires' disease organism was confirmed as the causative agent.
- Environmental or shared exposure during the convention, particularly the Monday morning activity, likely facilitated transmission.
