Hong Kong authorities find excessive levels of Legionella in MTR cooling towers after 11 people infected

The Centre for Health Protection has found excessive levels of Legionella bacteria in tested samples of cooling towers at Choi Hung MTR station following 11 infections in Wong Tai Sin, a nearby neighbourhood.

The water-dwelling bacteria causes Legionnaires’ disease which can lead to a fever, cough, headache, muscle pain and diarrhoea. Humans contract the disease – which can be lethal – by inhaling contaminated droplets. The incubation period is around two to 10 days. High-risk groups including people over the age of 50 and with weakened immunity. There is no known vaccine but the disease can be treated with antibiotics.

As of Thursday, the Centre for Health Protection has recorded 11 patients aged 65 to 84 as testing positive for Legionnaires’ disease in February.

The latest case involved an 82-year-old man who lived in Kam Hon House, Choi Hung Estate, Wong Tai Sin.

The Centre said it had conducted site visits with the Electrical and Mechanical Services Department to collect water samples and swabs from patients’ flats, the MTR station and the vicinity to investigate possible sources of infection. Water samples from three out of four freshwater cooling towers outside Choi Hung MTR station showed excessive levels of legionella, it said.

“We have suspended the operation of all four cooling towers,” MTR Operations Director Tony Lee told reporters.

Lee explained that the major functions of the towers were to cool down the air-conditioning system: “Their locations are outside of the station and do not impact indoor air,” he said.

The MTR Corporation has assigned contractors to clean and disinfect the cooling towers thoroughly in line with the Electrical and Mechanical Services Department maintenance guidelines, Lee said.

The towers were disinfected on February 4 and 12, however, the Centre will collect water samples again to check for any remaining bacteria, he added.

Choi Hung District Councillor Sean Mock told HKFP that he was concerned about the infections: “We spoke with the Housing Department on February 1, following two infections in Luk Ching House and Pak Suet House, and requested a thorough cleaning of the water tanks at the buildings, which was carried out the following day,” he said.

Mock said the district council has worked closely with MTR Corporation to limit the number of infections: “We are consulting professionals to see if further measures like a total shut-down of the MTR station would be necessary,” he said.

Lee added that as a preventative measure, ventilation systems at MTR stations have been maximised amid the novel coronavirus outbreak.