Update on investigation into case of Legionnaires' disease in elderly home

     The Centre for Health Protection (CHP) of the Department of Health today (December 5) reported an update on its investigations into a case of Legionnaires' disease (LD) in Kwong On Nursing Center in Aberdeen announced on November 30, and stressed again the importance of using and maintaining properly designed man-made water systems and that susceptible groups should strictly observe relevant precautions.

     Among the contacts identified by the CHP, a resident staying on the same floor as the previously announced patient was confirmed to have LD. The new case involved an 89-year-old female patient with underlying illnesses, who has developed decreased general condition, shortness of breath and cough on November 26, and was admitted to Queen Mary Hospital for management on the same day. She has been in stable condition and the clinical diagnosis was pneumonia.

     Her urine sample tested positive for Legionella pneumophila serogroup 1 antigen upon laboratory testing.

     Initial enquiries revealed that the patient had no travel history in the incubation period.

     "As legionellae are found in various environmental settings and aqueous environments, the sources of infection of these two patients are yet to be ascertained. Relevant water samples and environmental swabs have been collected from potential sources for testing. Epidemiological investigations are ongoing," a spokesman for the CHP said.

     The CHP has provided health advice against LD to staff and residents, including those with weakened immunity who should use sterile or boiled water for drinking, tooth brushing and mouth rinsing. Medical surveillance has been enhanced in collaboration with the elderly home. Tracing of contacts including staff and residents on the floor where the patients stayed in the incubation period is ongoing. The CHP will maintain close liaison with the elderly home to monitor the latest progress.

     Apart from the above institutional case, as of December 2, a total of 69 LD cases had been reported in 2017, comprising 63 community-acquired cases, two nosocomial cases, two institutional cases and two unclassified cases. In 2016 and 2015, there were 75 and 66 cases respectively.

     "Men, those 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 leading to stagnant water; living in areas with old water systems, cooling towers or fountains; using electric water heaters, whirlpools and spas or hot water spring spas; and recent stays in hotels or vessels," the spokesman said.

     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, whirlpools and spas, water fountains and home apparatus which support breathing. People may get 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. A shower may also generate small aerosols; and
  • If using these devices, fill the water tank with only sterile or cooled freshly boiled water, and not tap water. Also, clean and maintain them regularly according to manufacturers' instructions. Never leave stagnant water. 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;
  • Remove strainers in water taps and shower heads quarterly for cleaning;
  • 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) and they need to be changed periodically;
  • Drain and clean water tanks of buildings at least quarterly;
  • Drain or purge for at least one minute the 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 medical advice regarding the use and maintenance of home respiratory devices and use only sterile (not distilled or tap) water to clean and fill the reservoir. Clean and maintain them 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. Empty the water tank, keep all surfaces dry, and change the water daily; and
  • When handling garden soil, compost and potting mixes:
  1. Water gardens and compost gently using low pressure;
  2. Open composted potting mixes slowly and make sure the opening is directed away from the face;
  3. Wet the soil to reduce dust when potting plants; and
  4. 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.

Ends/Tuesday, December 5, 2017
Issued at HKT 17:30