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Hong Kong has recorded its first-ever locally acquired chikungunya fever case, with health authorities warning that the 10,000 people who live in the same neighbourhood as the 82-year-old patient face higher risks of infection. Authorities also announced on Sunday that citywide anti-mosquito work would be stepped up, especially around Fung Tak Estate in Diamond Hill, where the patient lived and was likely to have been bitten by virus-carrying insects. The patient developed pain in her ankle on October 18, which later spread to other joints, prompting her to visit the accident and emergency department at Kwong Wah Hospital in Yau Ma Tei. She was admitted to the hospital and is in a stable condition. The woman, who had not travelled outside Hong Kong in the past 1½ months, was diagnosed with the mosquito-borne disease on Thursday. The incubation period of the disease is two to 12 days. “Generally, the flying range of Aedes albopictus [mosquitoes] is short. We draw a circle centred on the block in which the patient lives, with a radius of 200 metres [656 feet]. Residents of flats within this range are at risk of infection if they are bitten by mosquitoes,” said Dr Albert Au Ka-wing, head of the communicable disease branch of the Centre for Health Protection. “The range involves around 20 residential buildings, with around 8,000 households.” Au estimated that the 8,000 households were home to more than 10,000 residents. The Department of Health said that the local case was Hong Kong’s first ever, as all previous infections recorded were imported. Before this year, Hong Kong last recorded cases of chikungunya fever in 2019, with 11 patients. Chikungunya fever is a viral disease transmitted by the Aedes mosquito. While rarely fatal, it can lead to symptoms such as fever, rash and joint pain. The residential sites potentially affected include seven blocks at Fung Tak Estate, Fung Chuen Court, Fung Lai Court and 11 other buildings west of Po Kong Village Road. Authorities will distribute leaflets and questionnaires to residents, calling on them to fill out the questionnaires and report to the centre if they have experienced any symptoms of chikungunya fever since October 1 to make sure there are no hidden cases. Three schools – Rhenish Church Grace School, St Bonaventure Catholic Primary School and AOG St Hilary’s College (Primary Section) – are also covered. “We will liaise with these schools [on Monday] … and see if there are any students with such symptoms. We will follow up if we find any,” Au said. Some residents of Fung Tak Estate expressed worries about the spread of the virus, saying that the area was infested with mosquitoes. “I’m quite worried … we elderly could easily get infected, but I have mosquito repellent at home,” said an old resident. Another resident said: “There are a lot of mosquitoes near the bus stop, and my children often get bitten … we will apply mosquito repellent when we go out, but there’s nothing else we can do.” A medical station has also been set up at Fung Tak Shopping Centre, where residents who suspect they may be infected can seek help. There is also a designated hotline set up. The Environment and Ecology Bureau will hold a meeting on Monday to coordinate the enhancement of anti-mosquito work across the city, while prevention measures in the patient’s neighbourhood will focus on eliminating adult pests and emptying stagnant water to curb reproduction. Centre for Health Protection controller Dr Edwin Tsui Lok-kin said: “We cannot rule out that there would be more cases in the near future as we are deliberately finding them out. “If we identify them early, we can send them to an environment with no mosquitoes as soon as possible and reduce the risk of transmission to an uninfected group.” He said Hong Kong had to see 12 consecutive days free of cases before concluding that the situation had stabilised and therefore authorities would re-evaluate the risk in mid-November. The area Gravidtrap index collected by the Food and Environmental Hygiene Department showed that the distribution of mosquitoes in Diamond Hill was not extensive in October, despite a slight increase from September. The government said the overall infestation index remained at a low level in October, after a substantial reduction from 9.5 per cent in June to 2.5 per cent in September. Hong Kong has recorded 46 imported chikungunya fever cases since January, including the first fatal one this year in which a 77-year-old man with chronic illnesses died. His clinical diagnosis was chikungunya fever complicated with multi-organ failure. According to Au, none of the imported cases had been near Fung Tak Estate, while the 82-year-old patient’s activity was largely confined to the area, which he said was likely to be where she caught the disease. It was therefore believed that a resident in the area had been infected with chikungunya fever, but only developed mild symptoms and did not see a doctor. The person might have been bitten by a mosquito, which in turn transmitted the virus to the patient in the current case, Au said.
