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An outbreak of Legionellosis at a business centre in Kuala Lumpur, 2013

Legionnaires’ disease was first described by Fraser et al. following an outbreak of pneumonia among the participants of the American Legion Convention in Philadelphia in 1976. It is caused by Legionella pneumophila, which is commonly found in aquatic environments. On 12th April 2013, Federal Territory State Health Department received notification of two cases working in the same office that were admitted into private hospital with similar respiratory symptoms. Investigation started immediately to identify the causative agents, source of outbreak and to recommend preventive and control measures.

A cohort study was conducted to identify the risk factors. Active case detection was carried out. All workers of the business centre were interviewed regarding the respiratory symptoms. Clinical samples were taken from workers with respiratory symptoms.

Results: A total of 1,365 workers were examined and 382 were defined as cases (attack rate 27.9%). Blood samples revealed 70 out of 188 (37.2%) samples were positive for IgM Legionella. The business centre was located in the middle of four high storey blocks. The cooling tower used a cross flow system and located at the rooftop of the block. Water samples from the cooling tower and fountain pool was positive for Legionella pneumophila Serogroup 1 and 2.

Conclusion: This Legionella outbreak was due to contaminated cooling tower system and fountain pool. The cooling tower was manually cleaned and tested negative post cleaning. The business centre authority was advised to clean the cooling tower and fountain pool regularly.

Source: https://www.e-mjm.org/2015/v70s1/mjm-sept-suppl-2154.html

3 comments

3 Comments

siraj munir

Apr 21

Causes and Transmission Legionella bacteria thrive in aquatic environments, particularly at temperatures between 20–50°C, with optimal growth at 35°C, as noted by WHO. They establish symbiotic relationships within protozoa and biofilms, making eradication challenging. Transmission occurs primarily through inhalation of aerosolized water droplets containing the bacteria, such as from showers, hot tubs, or cooling tower mist. Aspiration of contaminated water can also lead to infection, but person-to-person transmission is not observed. Risk factors, as highlighted by the Mayo Clinic (Mayo Clinic Legionnaires' Disease), include older age, smoking history, chronic lung disease, and impaired immune function.

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siraj munir

Apr 21

Replying to

Prevention and Control MeasuresPreventing Legionellosis involves rigorous management of water systems to limit bacterial growth:

Water System Maintenance: Regular cleaning, disinfection, and maintenance of cooling towers, spa pools, and hot water systems are critical. The WHO recommends maintaining hot water at ≥60°C at the heating unit and cold water at <20°C, with biocide treatment where necessary. Cooling towers should use frequent or continuous biocides and drift eliminators, while spa pools require chlorine levels and weekly draining/cleaning.
Building and Public Space Protocols: Implement water safety plans, as advised by WHO, including flushing unused taps weekly and taking extra precautions for hospital ice machines serving susceptible patients. The CDC (CDC Legionella Control) emphasizes water management programs in buildings and public hot tubs to reduce risk.
Home and Personal Measures: Avoid using tap water in respiratory therapy devices, and individuals at higher risk (e.g., elderly, smokers) should avoid high-risk exposures like contaminated hot tubs. Using genuine windshield cleaner fluid in motor vehicles, following manufacturer recommendations, is also advised to prevent contamination.

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