CHP announces investigation progress on Legionnaires' disease case
The Centre for Health Protection (CHP) of the Department of Health (DH) previously announced a Legionnaires' disease (LD) case involving a 45-year-old female. Based on further investigation findings, the CHP today (December 17) announced that the possibility of a nosocomial infection cannot be ruled out. The CHP has instructed the hospital concerned, St Paul's Hospital, to thoroughly disinfect the water system on the relevant floor. No other patients who stayed on the same floor developed symptoms of LD so far.
The female patient concerned had underlying illness and was immunosuppressed. She was admitted to a private room at St Paul's Hospital on November 19 for treatment of her underlying illness and was discharged on November 26. She was readmitted to the same hospital on November 28 for the same underlying illness. After re-admission, she developed a fever and her chest X-ray showed symptoms of pneumonia. Her respiratory specimen collected on December 2 tested positive for Legionella pneumophila serogroup 1. The patient's condition subsequently deteriorated and she succumbed on December 6 due to her underlying illness.
The St Paul's Hospital, Photo source: the official website of St Paul's Hospital
As the patient had stayed in the community and hospitalised at St Paul's Hospital during the incubation period, the CHP conducted environmental investigations at her residence and the hospital to investigate the source of infection. On December 5, the CHP and the Electrical and Mechanical Services Department collected water and environmental samples at the hospital. A total of 24 water samples were collected from wards of the floor where the patient was admitted between November 19 to 26. Upon laboratory testing by the Public Health Laboratory Services Branch of the CHP, 16 samples tested positive for Legionella pneumophila serogroup 1 at levels ranging from 0.9 to 7.3 colony-forming units per millilitre (cfu/ml), exceeding the action level for water supply systems in high-risk areas of hospitals (i.e. 0.1 cfu/ml or above). All 12 environmental samples tested negative.
The CHP also collected water and environmental samples from the patient's residence. Relevant laboratory testing is ongoing.
Taking into account the length of the patient's hospital stay, onset date and preliminary test results, the possibility of a nosocomial infection cannot be ruled out at this stage.
The patient had no household contacts. The CHP placed 28 patients admitted to the same floor concerned since mid-November under medical surveillance. No additional LD cases have been identified among the patients so far. All have been discharged.
St Paul's Hospital has closed and suspended use of the wards on the floor concerned and will thoroughly disinfect the water supply system on that floor as instructed by the CHP. Investigation is ongoing. The CHP has provided health advice and medical surveillance recommendations to the hospital, and will continue to closely monitor the implementation of the measures and conduct epidemiological investigations.
Legionellae are found in various environmental settings and grow well in warm water (20 to 45 degrees Celsius). They can be found in aqueous environments such as water tanks, hot and cold water systems, cooling towers, whirlpool spas, water fountains, humidifiers and home respiratory devices that support breathing. People may become infected when they breathe in contaminated droplets (aerosols) and mist generated by artificial water systems, or when handling garden soil, compost and potting mixes.
The public may visit the CHP's LD page, the Code of Practice for Prevention of LD and the Housekeeping Guidelines for Cold and Hot Water Systems for Building Management of the Prevention of LD Committee, and the CHP's risk-based strategy for prevention and control of LD.
The Centre for Health Protection
