Hot Topics: Should you worry about the melioidosis outbreak in Hong Kong? Here’s everything you need to know

Hong Kong has been dealing with a mysterious outbreak of melioidosis cases since August, with a cluster emerging in the Sham Shui Po district. It is an infectious disease caused by the bacterium Burkholderia pseudomallei. The bacterium is abundant in soils, especially moist clay, and muddy water.

As of November 2, 34 cases have been recorded in Hong Kong this year, with 23 found in the Sham Shui Po district. Seven deaths have been reported. The city logged 17 cases last year. An average of 10 cases have been detected each year over the past five years, according to official statistics.

Health authorities announced a plan to make melioidosis a statutory notifiable disease, meaning doctors would be required to report cases to officials. The Water Supplies Department said last month it had increased chlorine levels at the Sha Tin Water Treatment Plant to kill the bacteria that might have caused the outbreak. It was also considering installing UV light to eliminate more bacteria.

Respiratory disease specialist Dr Leung Chi-chiu said the chance of having a major outbreak was small as the disease was rarely transmitted from human to human.

Meanwhile, infectious diseases expert Dr Wilson Lam warned all Hong Kong residents, regardless of their medical condition, against using or consuming unboiled water found near soil that could be contaminated. He said the public should also avoid using such water for other purposes such as washing, rinsing mouths or brushing teeth.

He added that patients with chronic illnesses, especially diabetes, should be “extra careful”.

According to the Centre for Health Protection (CHP), the public can also take precautions such as wearing gloves and boots during activities that could involve contact with soil or water, washing or showering after exposure to possibly contaminated water or soil, cleaning wounds as soon as possible, covering cuts or grazes with waterproof dressings and washing hands with liquid soap after handling soil.
Staff writer

Question prompts:

• What were your first thoughts when you heard about the melioidosis outbreak, and why?

• Why is it important that melioidosis is made a statutory notifiable disease?

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Question prompts:

• What kind of clothing is the person in the photo wearing, and why?

• Using your answer above, what do you think the symbol in the photo represents, and why might it be applicable to Hong Kong?

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• The workers, aged 39 to 66, tested positive for antibodies of the bacterium Burkholderia pseudomallei after a serology test

• Health authorities revealed four soil samples from building site at Pak Tin Estate in Sham Shui Po contained bacterium

Ten asymptomatic workers from a contaminated construction site in Hong Kong tested positive for a bacterium that can cause melioidosis, health authorities revealed last month.

The Centre for Health Protection (CHP) said the workers, aged 39 to 66, tested positive for antibodies of the bacterium Burkholderia pseudomallei after a serology test.

The infected workers have been sent to hospital for treatment, the centre said, adding it was believed they had contracted the disease via contaminated soil or water. Tests on eight other workers came back negative, while screening of another eight provided inconclusive results and they would be checked again in two weeks.

Last month, health authorities revealed that four soil samples from the building site at Pak Tin Estate in Sham Shui Po contained the bacterium, but the CHP’s Dr Chuang Shuk-kwan assured the public that none of the cases known at the time had worked, entered or walked near the area.

Calcium hydroxide, which can be used as a disinfectant of the bacterium, has since been added to the soil at the construction site at Pak Tin Estate to protect workers and those living nearby.

Medical experts said the positive results only proved the workers had been exposed to the bacterium, adding they showed no symptoms of the disease. But further investigation would be needed to ascertain whether the construction site was the origin of the bacteria.

Respiratory disease specialist Dr Leung Chi-chiu said he believed that contamination at the building site was severe, given that 38 per cent of the workers tested were found to be infected.

“If workers at the site had such high exposure to the bacterium, it could not be excluded that residents of the public housing estate nearby were also heavily exposed,” he said. “The government should consider testing high-risk residents with a serology test to observe the rate of infection.”
Staff writers

Question prompts:

• Using News and Glossary, explain why an elderly resident living near Pak Tin Estate might be concerned after reading this article.

• Are the measures taken at the construction site at Pak Tin Estate sufficient? Why or why not? Explain using News and Glossary.

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• Source of infection unknown but several possibilities are highlighted, including bacterium entering reservoir through air vents

• We have to accept the disease has become endemic but there is no need to be too concerned, says one expert

The abnormal spate of melioidosis in Hong Kong might have originated from the bacterium found in the soil on top of a reservoir in West Kowloon after a government investigation found the DNA profiles were highly identical.

Revealing the findings early this month, a top microbiologist leading the investigation said it was unknown how the bacterium had been passed on to the patients, stressing the city’s fresh water was still safe.

“The tests conducted on water samples collected from the reservoir in Shek Kip Mei so far all tested negative,” Professor Yuen Kwok-yung from the University of Hong Kong said. “All we know is that the DNA [of patients and soil samples] are almost the same, and the soil samples were collected on top of the reservoir.”

Among the 471 environmental samples obtained from the area, 38 contained the bacterium, with 32 being collected from the soil on top of the reservoir. Four of the soil samples from the reservoir were genetically similar to the samples collected from the patients in the district.

Yuen said the team could not tell how it spread, despite conducting multiple inspections, but he highlighted several possibilities: bacterium entering the reservoir through the air vents; increase in water temperature lowering the chlorine levels in fresh water; more elderly people living in Sham Shui Po district; and global warming increasing the volume of Burkholderia pseudomallei in soil.

“The investigation has come to an end at this stage,” Yuen said. “We have to accept that the disease has become endemic ... the public need not be overly concerned if the cases do not share a common origin.”

Infectious diseases expert Dr Wilson Lam said there might be multiple sources of infection, including inhaling contaminated soil or drinking compromised water. Separately, respiratory medicine expert Dr Leung Chi-chiu suggested the authorities testing the elderly or those with chronic illnesses in Pak Tin Estate check whether they had been exposed as well.
Staff writers

Question prompts:

• Professor Yuen mentioned several possible ways melioidosis could spread. What do these possibilities suggest about city residents’ susceptibility to the disease?

• Based on your answer above, to what extent do you agree with Yuen that melioidosis has become endemic in Hong Kong, and why?

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Context

• What were your first thoughts when you heard about the melioidosis outbreak, and why? Shocked/stunned because Hong Kong is one of the places in the world that enjoys the safest drinking water. The Water Supplies Department has a comprehensive programme to monitor water quality and ensure that our drinking water complies with the Hong Kong Drinking Water Standards. (accept other reasonable answers)

• Why is it important that melioidosis is made a statutory notifiable disease? So that medical experts are aware of the various hotspots of diseases. This information lets them take steps to control the spread of infectious diseases to avoid epidemics and protect the health of the community. It also helps them improve health policy and check whether health services are working to the required standard.

Photo

• What is the person in the photo wearing? What might that tell you about the meaning of the symbol the person is holding? The person is wearing gloves, a face mask, and a white protective suit. These are typically worn to protect against something hazardous, like infectious diseases. Thus, the symbol likely indicates something hazardous. (accept other reasonable answers)

• Why might this symbol be relevant to the situation in Context? The symbol could be related to melioidosis because it will be made into a statutory notifiable disease, and the CHP recommends wearing gloves and boots when coming in contact with contaminated soil or water.

News

• Using News and Glossary, explain why an elderly resident living near Pak Tin Estate might be concerned after reading this article. Because the melioidosis cases reported between August and October were all located within a 1km radius of Pak Tin estate. In addition, individuals with underlying diseases including diabetes, lung disease, liver disease, renal disease, cancer or immunosuppression are more likely to be infected.

• Are the measures taken at the construction site at Pak Tin Estate sufficient? Why or why not? Explain using News and Glossary. They are not sufficient because the authorities have yet to determine the origin of the bacteria. In addition, the number of cases located within a 1km radius of Pak Tin is worrying. In my opinion, all residents/workers who have been within the 1km radius need to be tested and the affected construction site needs to be temporarily closed down until the source of contamination has been identified, especially since 38 per cent of the workers tested at the site were found to be infected.

Issue:

• Professor Yuen mentioned several possible ways melioidosis could spread. What do these possibilities suggest about city residents’ susceptibility to the disease? They are likely to be infected by the disease once it is present in the city’s reservoirs.

• Based on your answer above, to what extent do you agree with Yuen that melioidosis has become endemic in Hong Kong, and why? Given that the authorities are unable to tell how the disease spread after multiple inspections, it is fair that the population has no choice but to accept that it has become endemic. However, due to the various ways the disease could spread, this does not mean investigations should come to an end because there might be a lot of asymptomatic cases within the population and timely checks have to be conducted on the city’s water supply. (accept other reasonable answers)