Legionnaires' disease outbreak linked to a cold-water source in Yorkshire, 2022

Area of Science:

• Environmental microbiology
• Public health
• Infectious disease epidemiology

Background:

• Legionnaires disease outbreaks are a significant public health concern.
• Contaminated water systems are a common source of Legionella bacteria.
• Identifying the specific source is crucial for effective outbreak control.

Purpose of the Study:

• To investigate an outbreak of Legionnaires disease in a private residential setting.
• To identify the source and contributing factors of the outbreak.
• To evaluate challenges in implementing control measures and the role of enforcement.

Main Methods:

• Microbiological testing of clinical and environmental samples.
• Case ascertainment for confirmed and probable Legionnaires disease cases.
• Environmental assessment of the cold-water system for conditions conducive to bacterial growth.

Main Results:

• Legionella pneumophila was exclusively detected in the cold-water system.
• Two confirmed and one probable case of Legionnaires disease were identified.
• Favorable growth conditions included system 'dead legs' and heat transfer to the cold-water system.

Conclusions:

• Exclusive cold-water sources can harbor Legionella pneumophila.
• System design flaws and heat transfer facilitate bacterial proliferation.
• Effective control requires addressing environmental factors and utilizing enforcement powers when necessary.