Hong Kong’s first local chikungunya case this year: Tai Kok Tsui woman sought care only after nine days of fever

A 55-year-old woman with no travel history contracted chikungunya at home and in two parks below her building in Tai Kok Tsui. She developed a fever on September 7 but did not go to the Queen Elizabeth Hospital accident and emergency department until September 16 — a gap of nine days. A review of how the Centre for Health Protection handled two other local cases last year showed that one patient was admitted the day after developing typical symptoms including fever, while the other was admitted on the same day. The latest case involved a delay of considerably more than a day.

The Centre for Health Protection announced yesterday (September 17) that Hong Kong’s first local chikungunya infection of the year involved a 55-year-old woman living on Li Tak Street in Tai Kok Tsui. She developed a fever and headache on September 7, followed by joint pain in her fingers and wrists and a rash on her face and body. She sought treatment at Queen Elizabeth Hospital on September 16 and was admitted that day for treatment in a mosquito-free environment. A blood sample later tested positive for the virus. The centre’s epidemiological investigation found that her incubation period was from August 26 to September 5. She had not travelled abroad during that period, spent most of her time at home and recalled being bitten by mosquitoes at her residence and around Cherry Street Park and Lok Kwan Street Park.

Exactly 10 days passed between the onset of symptoms and the centre’s announcement. That 10-day period is not an abstract figure. According to international public health agencies, people with chikungunya generally become infectious around two days before symptoms appear and remain infectious for about five to seven days. If they are bitten by mosquitoes during this period, the insects may transmit the virus to other people. In other words, after developing a fever on September 7 and until her admission on September 16, the patient continued to spend time at home and in nearby parks, theoretically creating conditions for the virus to spread through mosquitoes. The Centre for Health Protection and the Food and Environmental Hygiene Department did not begin vector investigations and mosquito-control work until after she was confirmed to have the infection.

The timeline was notably different in last year’s cases. On October 18, an 82-year-old woman living at Fung Tak Estate in Wong Tai Sin first developed swelling and pain in her left ankle. She developed a fever and pain in the joints of her hands and feet on October 22, consulted a private doctor that day and was transferred to Kwong Wah Hospital the following day (October 23). On November 10, a 68-year-old woman living at Tung Hei Court in Shau Kei Wan first experienced joint pain, followed by fever and a rash on November 11. She sought medical attention and was admitted to hospital on the same day. In both cases, only zero to one day passed between the onset of typical fever symptoms and hospital admission. The nine-day gap in the Tai Kok Tsui case is unusually long among similar cases.

One possible explanation — although the Centre for Health Protection has not disclosed details of the individual patient’s diagnostic process, and the following is this newspaper’s inference based on the known timeline — is that the absence of a travel history offered no clinical clue of a local infection. Doctors may therefore have found it more difficult to consider chikungunya at the initial consultation, as the mosquito-borne disease has traditionally been associated with overseas travel, resulting in a delay in referral for laboratory testing.

Hong Kong recorded 82 confirmed chikungunya cases last year, 11 of them locally acquired. They were reported in areas including Wong Tai Sin, Shau Kei Wan, Tsing Yi and Sheung Wan, showing that sporadic transmission chains exist in the community. So far this year, there have been three cases, comprising this local case and two imported cases.

The Centre for Health Protection will set up a health station from today (the 18th) at the ground floor of Tai Kok Tsui Municipal Services Building, 63 Fuk Tsun Street, Tai Kok Tsui. It will provide health assessments for people with symptoms from 10am to 5pm. The hotline, 2125 2373, operated until 8pm today (the 17th) and will run from 9am to 6pm from tomorrow. The centre urged people living in, or who had visited, the areas around Li Tak Street, Cherry Street Park and Lok Kwan Street Park in Tai Kok Tsui to seek medical attention as soon as possible or call the hotline if they had developed a fever, rash or joint pain since August 1.