DH announces latest situation regarding Legionnaires' disease cases
The Centre for Health Protection (CHP) of the Department of Health (DH) today (October 12) reported the latest number of Legionnaires' disease (LD) cases, and reminded the public of the importance of using and maintaining properly designed man-made water systems, adding that susceptible groups should strictly observe relevant precautions.
From October 4 to October 10, the CHP recorded four LD cases, involving four males aged between 69 and 77. All of them had underlying illness. Details are as follows:
Locally acquired cases
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- a 76-year-old male living in Sha Tin District;
- a76-year-old male living in Kwun Tong District; and
- a77-year-old male living in Kwai Tsing District.
Case with place of infection to be determined
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- a 69-year-old male living in Kowloon City District. He travelled to the Chinese Mainland during the incubation period. Further investigation is needed to determine whether this is an imported or community-acquired case.
The CHP is conducting epidemiological investigations to identify the potential sources of infection and high-risk exposure. An initial investigation revealed that the aforesaid cases are sporadic cases. No epidemiological linkages have been established between these cases and other confirmed cases previously recorded in Hong Kong.
As of October 10, 157 LD cases had been recorded this year. In 2025 and 2024, there were 167 and 135 LD cases respectively.
Men, people aged over 50, smokers, alcoholics and persons with weakened immunity are more susceptible to LD. Some situations may also increase the risk of infection, including poor maintenance of water systems; living in areas with old water systems, cooling towers or fountains; using electric water heaters, whirlpool spas or hot water spring spas; and recent stays in hotels or ships.
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.
Immunocompromised persons should:
- Use sterile or boiled water for drinking, tooth brushing and mouth rinsing;
- Avoid using humidifiers, or other mist- or aerosol-generating devices; and
- If using humidifiers, or other mist- or aerosol-generating devices, fill the water tank with only sterile or cooled freshly boiled water, and not water directly from the tap. Also, clean and maintain humidifiers/devices regularly according to manufacturers' instructions. Never leave stagnant water in a humidifier/device. Empty the water tank, wipe all surfaces dry, and change the water daily.
The public should observe the health advice below:
- Observe personal hygiene;
- Do not smoke and avoid alcohol consumption;
- Strainers in water taps and shower heads should be inspected, cleaned, descaled and disinfected regularly or at a frequency recommended by the manufacturer;
- If a fresh-water plumbing system is properly maintained, it is not necessary to install domestic water filters. Use of water filters is not encouraged as clogging occurs easily, which can promote growth of micro-organisms. In case water filters are used, the pore size should be 0.2 micrometres (µm) or less and the filter needs to be changed periodically according to the manufacturer's recommendations;
- Drain and clean water tanks of buildings at least quarterly;
- Drain or purge for at least one minute infrequently used water outlets (e.g. water taps, shower heads and hot water outlets) and stagnant points of the pipework weekly or before use;
- Seek and follow doctors' professional advice regarding the use and maintenance of home respiratory devices and use only sterile water (not distilled or tap water) to clean and fill the reservoir. Clean and maintain the device regularly according to the manufacturer's instructions. After cleaning/disinfection, rinse the device with sterile water, cooled freshly boiled water or water filtered with 0.2 µm filters. Never leave stagnant water in the device. Empty the water tank, keep all surfaces dry, and change the water daily; and
- When handling garden soil, compost and potting mixes:
- Wear gloves and a face mask;
- Water gardens and compost gently using low pressure;
- Open composted potting mixes slowly and make sure the opening is directed away from the face;
- Wet the soil to reduce dust when potting plants; and
- Avoid working in poorly ventilated places such as enclosed greenhouses.
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.
Additionally, as smokers and alcoholics are more susceptible to LD, the Government urges members of the public to quit smoking and avoid drinking. Members of the public may call the DH Integrated Smoking Cessation Hotline at 1833 183, which is answered by registered nurses who provide professional counselling and referrals to a wide range of free smoking cessation services. The public may also visit the smoking cessation thematic website (www.livetobaccofree.hk) for more information on smoking cessation. The DH has also developed and promulgated the Alcohol Screening and Brief Intervention tool to primary healthcare service providers to facilitate the early identification and management of at-risk drinkers. For information on alcohol-related harm, please visit the DH's Change for Health website.
The Centre for Health Protection. Photo source: reference image
