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A family cluster of Legionella pneumophila infections
M Castellani Pastoris1, E F Viganò, C Passi
1Department of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Rome, Italy.
Insights
Three family members developed Legionella pneumophila serogroup 1 (Lp SG1) infection, with two distinct environmental sources identified. This rare intrafamilial occurrence highlights potential household transmission risks.
Area of Science:
- Environmental microbiology
- Infectious diseases
- Public health
Background:
- Legionella pneumophila serogroup 1 (Lp SG1) is a significant cause of bacterial pneumonia.
- Intrafamilial transmission of Legionnaires' disease is exceptionally rare in published literature.
Observation:
- Three of four family members exhibited seroconversion to Lp SG1.
- The son presented with severe pneumonia; the father and daughter had mild, transient fevers.
- Lp SG1 was identified in home shower water, butcher shop tap water, and refrigerator condensation water.
Findings:
- Two potential infection sources were identified: home showering and contaminated condensation water aerosolization at a family butcher shop.
- The mother remained seronegative, suggesting individual susceptibility or differential exposure.
- The findings suggest multiple exposure routes within a single household environment.
Implications:
- This case underscores the importance of investigating household water systems for Legionella contamination, especially in multi-person households.
- The study highlights the potential for diverse environmental sources contributing to Legionella infections within a close social network.
- Further research is warranted to understand the dynamics of intrafamilial Legionella transmission and risk factors.
Abstract:
Three members of one single family of 4, the father, a son and a daughter, showed seroconversion against Legionella pneumophila serogroup 1 (Lp SG1). The son had a severe pneumonia, whereas the father and the daughter did not develop any other illness than mild and transient fever. A fourth member, the mother, remained seronegative. Lp SG1 was detected by a direct immunofluorescence test in water samples from the shower at home, in tap water in the family's butcher shop, and in condensation water from the ventilator of refrigerator cells in the shop. Two different sources of infection appear to have occurred: showering at home and an aerosol of contaminated condensation water. Reports of more than one case of legionella infection within a family seem to be extremely rare and have not been found in the literature.