Pontiac fever outbreak associated with a cooling tower.

Area of Science:

• Environmental microbiology
• Public health
• Infectious disease epidemiology

Background:

• Pontiac fever is a mild, flu-like illness caused by Legionella bacteria.
• Outbreaks are often linked to contaminated water systems, particularly cooling towers.
• Identifying the source and transmission route is crucial for preventing further spread.

Purpose of the Study:

• To investigate the cause and transmission of a Pontiac fever outbreak in a Manhattan office building.
• To identify the specific pathogen and its environmental source.
• To assess the effectiveness of control measures.

Main Methods:

• Epidemiological investigation including case finding and symptom analysis.
• Environmental sampling of the building's cooling tower and air intake system.
• Microbiological analysis of water and air samples for Legionella pneumophila.
• Serological testing and monoclonal antibody typing of bacterial isolates.

Main Results:

• A high attack rate (78%) of Pontiac fever was observed among building occupants.
• Legionella pneumophila serogroup 1 was identified in high concentrations in the dedicated cooling tower.
• Airborne transmission was confirmed via settle plates in the air intake and affected office.
• The organism was difficult to eradicate from the cooling tower.

Conclusions:

• The office building's cooling tower was the source of the Pontiac fever outbreak.
• Airborne dissemination from the cooling tower led to widespread infection.
• Effective disinfection and maintenance are critical for preventing Legionella outbreaks in building water systems.