Hong Kong has been dealing with the mosquito-transmitted chikungunya fever (CF) since early August this year, and the numbers have gradually risen to reach just under 50 cases so far. As of Sunday afternoon, October 26, we have now recorded the first locally acquired case of CF – that is, one where the patient got infected in Hong Kong instead of bringing in the virus after having been abroad.
With cases by the thousands just across the border in mainland China, the unfamiliar nature of the CF 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 recently. Here’s what you need to know about chikungunya fever, the symptoms, how to prevent it, and more.
How many people in Hong Kong have chikungunya fever?
As of October 27, there are 46 confirmed cases of chikungunya fever in Hong Kong. While the ages of patients range between eight and 82 years old, all cases have been imported – with the exception of this latest local case – and the majority of our CF carriers have travelled to Guangdong province in mainland China or Bangladesh.
How many people in Hong Kong have died of chikungunya fever?
One patient with CF has passed away in Hong Kong recently. The clinical diagnosis for this 77-year-old man was chikungunya fever complicated with multi-organ failure.
In general, severe symptoms and deaths caused by CF is quite rare, and the mortality rate is less than one in 1,000. According to government statistics, from the beginning of this year to September 30, 155 CF-related deaths have been reported across 40 countries and territories.
What are the details of Hong Kong’s local chikungunya fever case?
The local CF patient is a 82-year-old woman living in Diamond Hill’s Fuk Tak Estate. She started developing symptoms on October 18 and was admitted to Kwong Wah Hospital on October 23, where she is receiving treatment in a mosquito-free environment.
According to preliminary investigations, the patient had visited Qingyuan in Guangdong in late August, but did not travel during the CF incubation period, which means she caught the virus within Hong Kong from an infected mosquito. She has four household contacts who are all currently asymptomatic and under medical surveillance
What does the local case of chikungunya fever mean for Hong Kong?
In short, it now means that Hongkongers could be more likely to catch CF. A carrier who had caught and incubated the virus within Hong Kong would have taken longer to seek medical attention than someone who had travelled and started displaying symptoms soon after returning. Ever since being unknowingly infected, the patient could have been bitten by another mosquito which could have gone on to bite and infect other people.
Since our local case rarely left her neighbourhood, and none of Hong Kong’s previous imported CF cases were reported being near Fuk Tak Estate, the authorities believe that a resident of Diamond Hill had CF, only displayed mild symptoms, did not see a doctor, and was bitten by a mosquito which then transmitted the virus to the 82-year-old woman.
Around 10,000 people live in the same neighbourhood in Diamond Hill, and they carry a higher risk of infection. Dr Albert Au Ka-wing, head of the communicable disease branch of the Centre for Health Protection, explained to the South China Morning Post that the flying range of the Aedes albopictus mosquito is generally quite short, and residents who live within a 200-m radius of the block where the patient lives could be at risk of infection if bitten of mosquitoes. In densely packed Hong Kong, this range involves around 20 residential buildings containing roughly 8,000 households.
What are the Hong Kong authorities doing about chikungunya fever?
Health authorities in Hong Kong announced on Sunday that mosquito prevention measures would be stepped up, especially around Fuk Tak Estate. Leaflets and questionnaires are also being distributed to residents of Fung Tak Estate, Fung Chuen Court, Fung Lai Court, 11 other buildings west of Po Kong Village Road, and three schools in the area. By filling out the questionnaires, the hope is that any hidden cases can be found early, and sent to a mosquito-free environment so the risk of transmission can be reduced.
Meanwhile, mosquito prevention measures are continuing across Hong Kong, 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.
The authorities are also intensifying mosquito control measures at the residence of previous confirmed patients, as well as the locations they visited after showing symptoms. These include intensive fogging in the scrubby areas within a 250-metre radius of the relevant locations, which will kill adult mosquitoes, and inspecting the sites to remove stagnant water, apply insecticide, and dispose of containers that could accumulate water every week, which will prevent mosquito breeding
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.
Is chikungunya fever 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. Chikungunya fever is rarely fatal and even when death occurs in a patient, it is usually related to other coexisting health issues.
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. There is also no rapid test available to check if you have CF, so prevention is really the best course of action.
If you have fever or acute joint pain, especially after returning to Hong Kong from regions where mosquito-borne diseases are endemic, it’s best to seek medical advice promptly so they can keep you in a mosquito-free environment where there’s no chance of being bitten and spreading CF elsewhere in Hong Kong.
The Department of Health has also urged the public not to self-medicate if suspected of having chikungunya fever, particularly using aspirin or non-steroidal anti-inflammatory drugs like ibuprofen, as these can have serious side effects such as increased risk of haemorrhaging.
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).
How bad is the chikungunya fever situation in mainland China?
As of September 27, the World Health Organization has logged a total of 16,452 cases of CF in China, not including Hong Kong, Macau, and Taiwan. Cases have been reported in 21 cities, with Foshan logging a significant number – about 10,032 cases – but there have been no reported fatalities thus far. When we first published this guide in August, experts were already believing that as many as 30 to 70 percent of residents in Foshan’s Shunde may be infected by the chikungunya virus.
CF infections are mainly in the southern part of mainland China, within cities such as Guangzhou, Zhongshan, Dongguan, Jiangmen, Shenzhen, and Zhanjiang. However, some other provinces have also reported CF cases in September, such as Guangxi, Fujian, Hunan, Sichuan, and Hainan.
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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