More dengue infections possible, health officials warn, as Hong Kong confirms four local cases in one day

Patients, all in stable condition, do not live in same area, making it hard to judge if disease came from one source

PUBLISHED : Wednesday, 15 August, 2018, 11:01am
UPDATED : Wednesday, 15 August, 2018, 12:11pm

Hong Kong health officials warned of more possible infections on Tuesday after four local cases of dengue fever – an “unusually” high number – were confirmed within a day.

Over the past few years, more than 100 cases of the potentially deadly mosquito-borne disease have been reported in the city annually, with most of them imported. Only a few cases, or none at all, were locally contracted each year.

The first case confirmed on Tuesday involved a 17-year-old boy from Highland Park residential estate in Lai King. He complained of a fever, sore throat and muscle and joint pain on August 7, the Centre for Health Protection said.

The baseball lover, who had no recent travel history, had been practising at the pitches at Sai Tso Wan Recreation Ground in Lam Tin almost daily during the incubation period. He said there were a lot of mosquitoes at the site but did not recall being bitten.

The teenager was in a stable condition in hospital on Tuesday. His parents showed no symptoms.

The second case involved a 78-year-old man from Kwai Shing West Estate in Kwai Chung. He recalled being bitten by mosquitoes at Clear Water Bay Second Beach. He showed symptoms from August 2 and was later admitted to hospital.

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The patient in the third case was an 84-year-old woman from Hillside Road in Cheung Chau. She fell ill on August 7 and was admitted to hospital.

The last case involved a 76-year-old woman from Tsui Chuk Garden in Wong Tai Sin. She started to get sick on August 8 and was admitted to hospital within two days. She was a frequent visitor to the nearby Lion Rock Park and Fung Wong San Tsuen.

All three patients had underlying illnesses and had not travelled recently. They were in a stable condition.

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This was the first time the authorities had seen four locally contracted cases emerging within such a short period, Dr Wong Ka-hing, the centre’s controller said, calling the situation “unusual” and worthy of attention.

“Besides these four cases, we could not rule out that there might be more people who were infected but [have] not yet found out,” he said.

Wong noted that the patients did not live in proximity, and they did not frequent any overlapping areas in the city. It would be hard to judge whether they shared a source of infection, he said, and it was too early to say whether the disease had become an endemic one.

Food and Environmental Hygiene Department pest control officer-in-charge Lee Ming-wai said anti-mosquito workers would be sent to the patients’ homes and to areas in a 500-metre radius to kill adult mosquitoes on Wednesday.

Samples of the pests would be collected to help trace the source of the infections.

The department’s dengue fever ovitrap index recorded at Sai Tso Wan Recreation Ground and Lai King in June and July showed the presence of the disease vector, Aedes albopictus, or the Asian tiger mosquito. But routine surveillance did not find the species to be carrying the virus.

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The centre will conduct site visits to the patients’ homes and carry out active case finding for the second to fourth cases. Health talks will also be arranged near their homes.

People who have been near the above-mentioned areas and develop symptoms should call the centre’s hotline at 2125 1122.

Excluding these four cases, as of August 9, 55 imported cases had been recorded this year.

Last year, 101 imported cases were seen, with one local case. And in 2016, 120 imported cases and four local cases – in different months – were recorded.

In 2015, three local cases were reported in different months, along with 110 imported cases.

Additional reporting by Elizabeth Cheung