The Centre for Health Protection (CHP) of the Department of Health (DH) today (November 3) said that with regard to the melioidosis infection cases recorded in Sham Shui Po earlier, the latest epidemiological investigation results revealed that four soil samples collected at the lawn on the top of the fresh water service reservoirs (FWSRs) in the area are genetically highly similar with the bacteria isolated from the patients. However, all water samples at present (including those collected from relevant FWSRs and buildings where confirmed cases resided) tested negative. As such, the infection sources and relevant modes of transmission are still pending further investigation. Also, no new confirmed melioidosis infection cases had been recorded as at 5pm today. The onset date of the most recent case was October 17.

     In view of the melioidosis infection cases in Sham Shui Po, the CHP has collected a total of 471 environmental samples from October 10 to November 1, covering buildings and units where confirmed cases resided, nearby parks and construction sites, as well as Shek Kip Mei FWSRs, Butterfly Valley Fresh Water Primary Service Reservoir and Beacon Hill High Level FWSR. Among the environmental samples, all water samples tested negative. Apart from the two swab samples taken at household and four soil samples collected at the redevelopment construction site of Pak Tin Estate which tested PCR positive to Burkholderia pseudomallei, the CHP also found that 32 soil samples taken from the lawn on the top of relevant FWSRs tested PCR positive.

     The CHP has followed up with the team of the University of Hong Kong on the 32 aforementioned positive soil samples and yielded positive bacterial culture from six of the samples. The DH's Public Health Laboratory Services Branch completed whole genome sequencing for four of the samples and the sequencing results revealed that the bacteria of the environmental isolates and the human isolates are genetically highly similar. The genetic sequencing of the remaining two samples are underway.

     After examining the environmental investigation results, as all water samples currently collected (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. As such, experts and the CHP 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. For prudence sake, residents in Sham Shui Po, especially elderly and persons with underlying diseases, are advised to let tap water run for one minute before using it for brushing teeth, washing face or bath. They should not drink raw water. 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.

     The Government spokesman stressed that the Water Supplies Department (WSD) has all along adhered to stringent procedures in disinfecting and handling drinking water, and following guidelines of the World Health Organization, add appropriate amount of residual chlorine to treated water before supplying to the public, in order to kill bacteria and prevent the breeding of pathogens including Burkholderia pseudomallei during the supply process. The WSD's routine water quality monitoring also showed that the water supplied meets the Hong Kong Drinking Water Standards.

     In view of the positive bacterial culture result of samples taken from the soil in the vicinity of the Shek Kip Mei FWSRs to Burkholderia pseudomallei, although the water samples tested negative and fully meets the safety standard, the WSD has implemented additional measures to provide extra protection and to reassure the residents. The measures include:

• Increased the content of residual chlorine in water supplied to Sham Shui Po and ensure the residual chlorine content remains effective during the whole water supply process;
• Arrange immediate installation of high efficiency particulate air filters at the air vent and real-time residual chlorine monitoring device at outfall locations of the service reservoir, and to complete the installation gradually in the coming few days; and
• Further increase the frequency of checking water samples of the water supply system.

     Melioidosis is an endemic disease in Hong Kong, and the bacteria could exist in soil in general. In the past five years (2017 – 2021), the number of cases recorded in Hong Kong ranged from three to 17 every year. The CHP reminded members of the public that according to literature, infection cases are more common after typhoons or storms. The bacterium Burkholderia pseudomallei of melioidosis in the soil and muddy water may become exposed to the ground after typhoons or storms, and the bacteria would spread easier with strong wind or storms. As such, the number of melioidosis cases may increase. The CHP appealed to 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.

     To enhance surveillance against melioidosis cases, the CHP has been working closely with the Hospital Authority, and has reminded doctors in Hong Kong to enhance vigilance on suspected cases and promptly refer patients (especially those with chronic illnesses) to hospitals for treatment and report to the CHP according to the test result for the bacteria. The CHP will continue its epidemiological investigations on the cases in Sham Shui Po as well as other cases.

     The CHP will continue to deliver health messages to the local community and the general public via various channels, including health talks.

     ​The CHP reiterated that person-to-person transmission and animal-to-human transmission are rare, but Melioidosis bacteria can survive in the local environment and melioidosis cases have been recorded in Hong Kong each year. 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 3, 2022
Issued at HKT 22:37

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