Last week, Hong Kong recorded its first case of chikungunya fever since 2019, swiftly followed by three more confirmed cases by Wednesday, August 6. The unfamiliar nature of the virus, more commonly seen in South and Southeast Asia, is giving rise to a lot of questions and concerns among Hong Kong residents fearful of an outbreak.
From 2016 to 2019, the Centre for Health Protection (CHP) of the Department of Health recorded between one and 11 imported cases of chikungunya fever cases per year, with no new cases being reported in the city since then – until now, that is. Here’s what you need to know about chikungunya fever, the symptoms, how to prevent it, and more.
What is chikungunya fever?
Chikungunya fever is a mosquito-borne illness, transmitted to humans through the bite of the female Aedes mosquitoes, which carries the virus. Aedes albopictus, also known as the Asian tiger mosquito, is common in Hong Kong and can transmit chikungunya by biting affected individuals during the early stages of infection, when the patient still carries a large amount of the virus in their blood, and passing on the virus through further bites.
How did the Hong Kong patients get chikungunya fever?
A 12-year-old boy was reported to be Hong Kong’s first imported case of chikungunya fever since 2019. It is believed that he was infected in Foshan in Guangdong province between July 17 and 30, when he travelled to the Shunde district with his mother. Last week, the boy developed symptoms, and he was confirmed to have been infected with the chikungunya virus on Saturday, August 2, after being admitted to United Christian Hospital the previous day for treatment. His condition is now stable, the CHP reported.
On Wednesday, August 6, three more cases of chikungunya fever were confirmed in Hong Kong, all of them imported cases. A 79-year-old woman started experiencing symptoms after travelling to Foshan in July, while a 55-year-old man and his 10-year-old son developed symptoms around late July and early August after travelling to Bangladesh between July 12 and August 3.
Is it contagious?
Fortunately, chikungunya is not contagious between humans. Dr Edwin Tsui, controller of the CHP, said in an official press release that chikungunya fever ‘is not transmitted from person to person’, so it cannot be caught directly from an infected patient.
What are the symptoms?
Once bitten by a mosquito carrying the infection, patients will develop symptoms in the span of three to seven days. Similar to dengue fever, another mosquito-borne virus, chikungunya symptoms can manifest as a fever, rashes, inflammation, and joint pain, but the effects are reported to be milder than dengue fever. Individuals with weak immunity and other pre-existing health conditions may be more severely affected by chikungunya.
In most cases, symptoms begin to alleviate in about a week, but in severe cases of chikungunya fever, discomfort in the joints can last for months or even years.
How is chikungunya treated?
At the moment, chikungunya is treated with medication designed for relieving pain, fever, and inflammation, as there is no medicine or treatment that targets the virus specifically.
Is there a vaccine?
Not in Hong Kong at this time. A spokesperson for the CHP has shared that research into chikungunya vaccines is still ongoing. Wong Hoi-kei, senior medical and health officer of the CHP, said that ‘chikungunya vaccines are a relatively new thing, and they have not been widely used by any country and region.’ In the US, two chikungunya vaccines are on the market – however, these have not been approved for use in Hong Kong (yet).
Is there likely to be an outbreak in Hong Kong?
It’s too early to say if the chikungunya virus has already been locally transmitted within the city, though – with the high flow of travellers to and fro mainland China – it is likely that Hong Kong may see more imported cases in the coming days and weeks, which could lead to a greater risk of local transmission.
Meanwhile, the World Health Organization has raised concerns about the spread of the chikungunya virus and called for urgent action to prevent an epidemic. In an official government press release, Dr Tsui comments that environments with serious mosquito infestations can also lead to a large-scale outbreak of chikungunya.
Health authorities in Hong Kong are already gearing up to respond to the possibility of an increase in cases. Mosquito prevention measures are being put in place across districts, with targeted control actions being carried out at sites suspected of higher infestation risks to eliminate adult mosquitoes and mosquito breeding grounds, and remove stagnant water.
How bad is the chikungunya fever situation in mainland China?
Cases of chikungunya fever have surged in various places in mainland China, with Shunde district in Foshan logging a significant number – about 5,660 cases as of last week – but there have been no fatalities thus far. Foshan has recorded more than 7,000 chikungunya fever cases since July, and the outbreak is still ongoing. Experts believe that as many as 30 to 70 percent of residents in Shunde may already be infected by the chikungunya virus. Infections in 12 other cities in Guangdong province, such as Guangzhou, Zhongshan, and Dongguan, have also been reported, with Chinese authorities sharing updates that all reported cases have been mild and patients are recovering.
What to do to prevent it
Avoiding mosquito bites is going to be the best way to prevent potential infection, so layer up on insect repellant and DEET, and wear loose clothing that covers your arms and legs. Removing stagnant water or potential mosquito breeding grounds in your home and frequently occupied spaces will also go a long way.
As there are no widely used rapid testing kits available for chikungunya fever, the CHP urges individuals who develop symptoms or have recently returned from places with notable chikungunya cases to consult a medical professional as soon as possible to aid in early identification and safeguard public health to minimise risk of local transmission.
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