The Centre for Health Protection (CHP) of the Department of Health (DH) today (November 17) said that with regard to the melioidosis infection cases recorded in Sham Shui Po earlier, the latest epidemiological and environmental investigation results revealed that all water samples tested negative, while another 93 environmental samples collected from November 3 to 9 tested PCR positive.

     Also, one new confirmed melioidosis infection case had been confirmed by the DH's Public Health Laboratory Services Branch (PHLSB) today, involving a 61-year-old male with diabetes living in Sham Shui Po. He developed fever and malaise and attended the Accident and Emergency Department of Caritas Medical Centre on November 6, and was admitted on the same day. His clinical diagnosis was chest infection. He is still being hospitalised and his current condition is stable. His sputum specimen was confirmed positive for Burkholderia pseudomallei by the PHLSB today. A total of 37 melioidosis infection cases had been recorded in Hong Kong so far this year, among which 21 cases living in Sham Shui Po were recorded since August.

     In view of the melioidosis infection cases in Sham Shui Po, the CHP has conducted large-scale environmental investigations in the district. A total of 471 environmental samples have been collected from October 10 to November 1. Among them, 38 samples tested PCR positive to Burkholderia pseudomallei, including two swab samples taken at household, four soil samples collected at the redevelopment construction site of Pak Tin Estate, and 32 soil samples taken from the lawn on the top of relevant fresh water service reservoirs (FWSRs). Relevant results have been announced on November 3 (www.info.gov.hk/gia/general/202211/03/P2022110300829.htm?fontSize=1). With regard to the 32 soil samples, the team of the University of Hong Kong (HKU) yielded positive bacterial culture from seven samples. The whole genome sequencing conducted by the DH's PHLSB revealed that the bacteria of the environmental isolates and the human isolates of some patients are genetically highly similar.

     As the soil samples of the relevant FWSRs tested positive for Burkholderia pseudomallei bacteria, the CHP continued to conduct further environmental investigation with the HKU team and collected over 200 environmental samples from November 3 to 9 (including water samples at the FWSRs, swab samples of the exposed part of the ventilator at the top of the FWSRs, soil samples near the ventilator as well as swab samples at the top of the FWSRs). All water and swab samples collected from water of the FWSRs tested PCR negative, showing that water in the FWSRs has not been contaminated. Also, among the samples, 87 soil samples collected at Shek Kip Mei and Butterfly Valley FWSRs, five swab samples collected at the ventilator of Shek Kip Mei FWSR, and one environmental swab sample collected near the ventilator of Shek Kip Mei FWSR tested PCR positive to Burkholderia pseudomallei. All the six swab samples have however negative bacterial culture, showing no live bacteria could be found.

     The CHP reiterated that all water samples collected during the investigation so far (including those from relevant FWSRs and the water meters at the residential units of confirmed cases) tested negative, showing that the pipes and water of the FWSRs have not been contaminated by the environment. According to data of the Water Supplies Department (WSD), no abnormalities were found in the routine water quality monitoring of drinking water samples in relevant service reservoir and the district in the past year, and the relevant quality fully met the Hong Kong Drinking Water Standards (HKDWS). In view of the epidemiological and environmental investigation results, the CHP and experts considered that there is no evidence to suggest the infections of the cases are related to tap water supplied by relevant FWSRs. The modes of transmission could not be ascertained.

     A Government spokesman pointed out that, melioidosis is an endemic disease in Hong Kong and this type of bacteria exists in the environment. The recent number of confirmed cases has dropped when compared with that in August to October. The Government has included melioidosis as a statutorily notifiable infectious disease on November 11. The CHP would enhance its surveillance and prevention work as well as to intervene early should there be any suspected outbreak identified in the community

     Members of the public should avoid contact with contaminated soil, and wear appropriate protective clothing or footwear when participating in activities with possible contact with soil or water. They should wash hands with liquid soap and water after handling soil or gardening. They should also clean any wounds as soon as possible and cover any cuts or grazes with waterproof dressings. Taking into account that more cases were recorded in Sham Shui Po, the CHP continues to advise, for prudence sake, residents in Sham Shui Po, especially elderly and persons with underlying diseases, to let tap water run for one minute before using it for brushing teeth, washing face or bath. They should not drink raw water.

     The spokesman stressed that the WSD has all along adhered to stringent procedures in treating drinking water and routine water quality monitoring of fresh water supply to different districts are in place to ensure the water quality fully complies with the HKDWS. The WSD uses chlorine to disinfect drinking water. To prevent the growth of bacteria during the distribution, the WSD follows guidelines of the World Health Organization to add appropriate amount of residual chlorine to drinking water so that it would be difficult for pathogens including Burkholderia pseudomallei to survive in the pipes. Although the water quality for public consumption fully complies with the HKDWS, the WSD has earlier implemented prudent measures to reassure members of the public. The measures include:

• Increased the content of residual chlorine in drinking water in all water supply zones in Hong Kong to provide extra protection to the public;
• Completed the installation of filters at the ventilators of the relevant FWSRs in Sham Shui Po and is arranging to install filters at all of the about 2 400 ventilators of its remaining 175 FWSRs, which is targeted to complete within two months;
• Installed real-time residual chlorine monitoring systems at outlets of the FWSRs in Sham Shui Po. Such device would be installed at FWSRs in other districts on a risk-based strategy according to needs.
   

     ​The CHP opined the above-mentioned measures by the WSD could effectively prevent the drinking water supplied by the FWSRs from Burkholderia pseudomallei contamination. The CHP appealed again to members of the public to seek medical advice if they develop symptoms, in particular people with diabetes or other immunocompromised conditions, in order to receive appropriate medical diagnosis and treatment. The CHP will continue to deliver health messages to the local community and the general public via various channels. For more information on melioidosis, please visit the website of the CHP at www.chp.gov.hk/en/healthtopics/content/24/101110.html.

Ends/Thursday, November 17, 2022
Issued at HKT 20:45

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