Hong Kong has confirmed its first imported case of chikungunya fever since 2019. The case involves a 12-year-old boy and has prompted health authorities to urge residents to be more vigilant against this mosquito-borne disease.
Should residents be concerned about a potential local outbreak? What preventive measures should be taken? The South China Morning Post provides a detailed breakdown of the situation for you.
1. What happened to the boy?
The head of the communicable disease branch of the Centre for Health Protection, Dr Albert Au Ka-wing, said the boy lived in Kwun Tong’s On Tat Estate and was diagnosed with the disease after returning from mainland China.
He travelled with his mother to Foshan’s Shunde district, where an outbreak is ongoing, from July 17 to 30 and reported being bitten by mosquitoes while outside. He developed a fever, rash and joint pain on Thursday and was confirmed to be infected on Saturday morning after being admitted to United Christian Hospital.
The government said on Sunday that the boy had been transferred to Princess Margaret Hospital in Kwai Chung and remained in a stable condition. His household contacts were currently asymptomatic and under medical surveillance.
The Housing Authority and the Food and Environmental Hygiene Department stepped up anti-mosquito efforts at Kwun Tong’s On Tat Estate and United Christian Hospital over the weekend.
The measures include setting up more traps, applying larvicidal oil in breeding spots, clearing stagnant water and grass near drainage holes, strengthening disinfection and conducting outreach efforts to remind residents to clean water from flower pots.
2. What are the symptoms? Is it fatal?
Chikungunya fever’s symptoms are similar to those of dengue fever and include fever, rashes and joint pain, particularly in the hands and feet. A key difference is that chikungunya fever is generally milder than dengue, which can lead to more severe conditions like haemorrhagic fever.
The medical director of the Hospital Authority’s infectious disease centre, Jacky Chan Man-chun, said severe complications and death from chikungunya were “extremely rare”.
According to the World Health Organization, they usually occur in young babies or elderly people with other coexisting health problems.
The disease is transmitted through bites from the Asian tiger mosquito. Photo: zb/dpa
3. Which mosquitoes spread the virus?
The virus is spread through the bites of infected mosquitoes and is not transmitted from person to person through daily social contact.
Two types of mosquito can transmit the virus: the Aedes aegypti, or yellow fever mosquito; and the Aedes albopictus. The Aedes albopictus, or the Asian tiger mosquito, is a very common species found in Hong Kong.
4. What preventive measures should I take if travelling?
Officials stressed that the disease is preventable by avoiding mosquito bites. Travellers are advised to take full personal protective measures, including using mosquito repellent.
To protect yourself from mosquito bites when travelling, you should wear loose-fitting, light-coloured, long-sleeved tops and long trousers.
It is also essential to apply an insect repellent containing DEET to any exposed skin and onto your clothing. For pregnant women and children aged six months or older, DEET products are usable, but it is recommended to adhere to a concentration limit of 30 per cent for pregnant women and 10 per cent for children.
For additional outdoor protection, avoid using cosmetics or skincare products with a fragrance. Remember to reapply insect repellent as directed by the product instructions. Apply sunscreen before repellent if using both.
Taking general measures to prevent mosquitoes from breeding in your vicinity is also a key part of staying protected.
5. What should I do if I display symptoms?
Anyone who develops symptoms after returning from an affected area should seek medical advice promptly and, crucially, tell their doctor their travel history. The government provides free testing for suspected cases, which requires a blood sample sent to a laboratory.
Officials also strongly advise that anyone returning from affected areas should continue to use mosquito repellent for 14 days upon arrival to prevent any potential transmission to local mosquitoes, even if they do not have symptoms.
The head of the Food and Environmental Hygiene Department’s rodent risk assessment and advisory unit, Anita Fok (from left), the head of the communicable disease branch of the Centre for Health Protection, Albert Au, and the medical director of the Hospital Authority’s infectious disease centre, Jacky Chan. Photo: Edmond So
6. How long will a patient take to recover?
Most patients recover on their own without specific antiviral medication. The 12-year-old patient’s fever and joint pain had already disappeared by Saturday morning, with only a mild rash remaining. However, in some high-risk individuals such as the elderly, joint pain can persist as a long-term symptom.
According to expert Yuen Kwok-yung of the University of Hong Kong, the joint inflammation and swelling can persist for more than three months in about 40 per cent of patients.
7. Are there any vaccines available?
Two new vaccines exist globally, but both are very new and not yet widely used, Au said. The World Health Organization is still reviewing their safety and efficacy data, and they are not currently registered for use in Hong Kong.
8. Any chance of an outbreak in Hong Kong?
The risk of small-scale local transmission is a possibility, especially as mild cases may go undiagnosed. A mosquito can spread the virus as quickly as two days after biting an infected person, much faster than the eight days required for dengue, which allows for rapid transmission where populations have no immunity.
The risk of further imported cases was considered high due to frequent summer travel between Hong Kong and Guangdong, Au said, adding that the government had been preparing for several weeks.
“We do not rule out that with some imported cases, there may be some local transmission in Hong Kong,” Au said. “The risk is medium to high.”
However, officials said the risk of a widespread outbreak or the disease becoming endemic was “extremely low”, thanks to a robust surveillance system and improved local mosquito control this year compared with the past two years.
The head of the Food and Environmental Hygiene Department’s rodent risk assessment and advisory unit, Anita Fok Ming-yan, said teams had already begun intensive mosquito control work around the patient’s home and hospital.
“We again appeal to the public to strengthen anti-mosquito work in their own premises,” she said.
