In a follow-up on the increase in melioidosis cases in Hong Kong this year, the Centre for Health Protection (CHP) of the Department of Health reports as of yesterday (October 17), the CHP recorded a total of 29 melioidosis cases this year so far, involving 21 males and eight females, aged from 42 to 93 years, and 20 of them live in Sham Shui Po (17 of which were recorded in or after August). Initial epidemiological investigations revealed that majority of the patients are with underlying diseases or immunocompromised while none of their household contacts developed symptoms. The patients had not visited any places in common prior to their onset nor have they drunk unboiled water. Transmission by food or products can be ruled out at this stage.
The CHP has collected a total of 107 environmental samples in Sham Shui Po (including 16 soil samples from nearby parks and construction sites; 90 water samples and environmental swap samples taken from 16 buildings where confirmed cases since August resided; and one ash sample from a household). All the samples tested PCR negative to Burkholderia pseudomallei.
Meanwhile, the CHP has invited the Chair Professor of the Department of Microbiology of the University of Hong Kong (HKU), Professor Yuen Kwok-yung and his team to join the environmental investigation. The HKU team has collected 31 environmental samples from some of the confirmed cases’ residence, among which two swab samples (one taken from the tap of the bathroom and one from the inner surface of a vase) from a household tested PCR positive to Burkholderia pseudomallei. The CHP learnt that the PCR test method deployed by the HKU team has a very high sensitivity and the two positive samples carried very small amount of the bacteria, which could be the residual gene fragment of the bacteria. The possibility that the relevant environment was contaminated by the bacteria shedded by the patient cannot be ruled out.
After examining the environmental investigation results, the CHP considered that there is no evidence at the present moment to suggest the source of infection of the cases came from tap water. However, in view of the HKU’s positive findings, as a precautionary measure, the CHP has notified the Water Supplies Department (WSD) to examine the water supply system in the district and also the maintenance records for the past three months. The WSD has not found any events of contamination of water supply system by foreign objects in the district over the past three months. No abnormalities were found in the testing of water samples in relevant service reservoir and district and the test results fully met the Hong Kong Drinking Water Standards.
After the announcement on case details on October 12, the CHP have not received notifications from the Hospital Authority (HA) on record of new cases so far. Meanwhile, the CHP has informed all doctors and private hospitals in Hong Kong of the relevant situation in its letter on October 14 and reminded them to take note of the suspected cases. The CHP has also enhanced its surveillance against melioidosis cases together with the HA.
A spokesman for the CHP said that melioidosis bacteria can survive in the local environment and that melioidosis cases have been recorded in Hong Kong each year. 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 expose 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 cannot rule out the possibility that the cases in the past few months are related to the weather conditions.
The CHP again reminds members of the public, especially high risk groups such as persons with underlying diseases, to avoid contact with soil or muddy water after storms and heavy rain to prevent melioidosis infection. Person-to-person and animal-to-human transmission are rare. Members of the public should seek medical advice promptly if they develop symptoms.
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