Update on mosquito-borne diseases, chikungunya fever and dengue fever
*********************************************************************
Chikungunya fever
As of 5pm today, two new cases of CF had been recorded.
The first case involves a 62-year-old female living in Kowloon City District. Preliminary investigation revealed that she visited Foshan in Guangdong Province alone between August 26 and September 17. She developed joint pain on September 15 and then fever and rash on September 17. She sought medical attention at a General Out-patient Clinic on September 18. Her blood sample tested positive for the CF virus upon laboratory testing. She has been arranged for treatment in Queen Elizabeth Hospital in a mosquito-free environment. She is now in stable condition. She has no household contacts.
The other case involves a 26-year-old male living in Central and Western District. Preliminary investigation revealed that he visited Guangzhou in Guangdong Province between September 12 and 17, and to Foshan on September 13 and 15 as a day trip. He developed a fever, joint pain and rash on September 16. He attended a private clinic and the Accident and Emergency Department of Queen Mary Hospital on September 18 and was admitted on the same day for treatment in a mosquito-free environment. He is now in stable condition. His blood sample tested positive for the CF virus upon laboratory testing.
The patient's two household contacts, who are also their travel collaterals, are currently asymptomatic and under medical surveillance.
Since the two patients stayed in Guangdong Province during their incubation periods, the CHP considered that they were infected during travel. The cases were classified as imported. The CHP's epidemiological investigation is ongoing, and it has reported the cases to the health authority of Guangdong Province.
So far this year, Hong Kong has recorded a total of 21 confirmed CF cases. All are imported cases. From 2016 to 2019, Hong Kong recorded between one and 11 imported cases annually.
Since the beginning of 2025, and as of August, approximately 317 000 CF cases and 135 CF-related deaths have been reported in 16 countries/territories. Cases have been reported in the Americas, Africa, Asia, and Europe. CF outbreaks currently occur in many countries worldwide. Members of the public should check the situation of the destinations before travelling abroad.
Dengue fever
From September 12 to yesterday (September 18), the CHP recorded one imported DF case. The patient had travelled to Qingyuan in Guangdong Province during the incubation period.
As of yesterday, 48 imported DF cases have been recorded so far this year. A total of 161 cases of DF were recorded in 2024, including 156 imported and five local cases.
According to the World Health Organization (WHO), the global incidence of DF has markedly increased over the past two decades, posing a substantial public health challenge. In 2023, over 6.5 million cases and more than 7 300 dengue-related deaths were reported in over 80 countries/territories. In 2024, the WHO recorded over 14 million cases, which was a record number.
DF is prevalent in many neighbouring tourist destinations. Indonesia, India, Malaysia, Thailand and Vietnam have each recorded over 40 000 cases so far this year. Singapore has also recorded over 3 000 cases. Meanwhile, according to the Guangdong Provincial Center for Disease Control and Prevention, Guangdong Province has recorded over 1 300 locally infected cases so far this year. A total of 129 cases were recorded in a week between September 8 and 14, with the highest number of cases recorded in Guangzhou, Shenzhen, Chaozhou, Zhongshan and Jiangmen.
Detailed information on the latest DF situation in Hong Kong, as well as neighbouring and overseas countries and areas, has been uploaded to the CHP website.
Continuously strengthening prevention and control
The Food and Environmental Hygiene Department (FEHD) continues to conduct vector investigations and targeted mosquito control operations, and intensify mosquito prevention and control measures at the residences of recently confirmed patients of CF and DF, as well as at locations visited after the onset of symptoms. These measures include:
- carrying out intensive fogging in scrubby areas within a 250-metre radius of the relevant locations to kill adult mosquitoes;
- carrying out inspections of the locations, removing stagnant water, applying insecticides and disposing of abandoned water containers every week with a view to preventing mosquito breeding; and
- enhancing public education efforts through organising health talks, setting up mobile education stations, and distributing publicity leaflets.
The CHP urged schools to follow the FEHD's anti-mosquito guidelines to strengthen efforts to clear stagnant water on school premises and eliminate mosquito breeding sites. It is also imperative to remind staff members and students to consistently implement mosquito prevention and personal protective measures to guard against the spread of mosquito-borne diseases within school premises.
Additionally, the CHP's Port Health Division continues to step up inspections at boundary control points and to remind cross-boundary public transport operators and other relevant parties to ensure good environmental hygiene and effective implementation of anti-mosquito measures. Furthermore, staff members of the Port Health Division distribute leaflets to travellers, conduct temperature screenings for inbound travellers, conduct health assessments for travellers with fever or related symptoms and refer them to hospitals for follow-ups when necessary.
Proper use of DEET-containing insect repellents or other effective active ingredients can prevent mosquito bites, but the following precautions should be taken when using them:
- read the label instructions carefully first;
- apply right before entering an area with a risk of mosquito bites;
- apply on exposed skin and clothing;
- use DEET of up to 30 per cent for pregnant women and up to 10 per cent for children (For children who travel to countries or areas where mosquito-borne diseases are endemic or epidemic and where exposure is likely, those aged 2 months or above can use DEET-containing insect repellents with a DEET concentration of up to 30 per cent);
- apply sunscreen first, then insect repellent;
- reapply only when needed and follow the instructions; and
- in addition to DEET, there are other insect repellents available on the market containing different active ingredients, such as IR3535 and picaridin. When using any insect repellent, the public should follow the usage instructions and precautions on the product label.
The FEHD also appeals to members of the public to continue to stay alert and work together to carry out mosquito prevention and control measures early, including inspecting their homes and surroundings to remove potential breeding grounds, changing water in vases and scrubbing their inner surfaces, removing water in saucers under potted plants at least once a week, and properly disposing of containers such as soft drink cans and lunch boxes. The FEHD also advises members of the public and estate management bodies to keep drains free of blockage and level all defective ground surfaces to prevent the accumulation of water. They should also scrub all drains and surface sewers with an alkaline detergent at least once a week to remove any mosquito eggs.
The public should call 1823 in case of mosquito problems, and may visit the following pages for more information: the CF page of the CHP and the Travel Health Service, the latest Travel Health News, tips for using insect repellents, and the CHP Facebook Page, Instagram Account and YouTube Channel, and also the Mosquito Prevention and Control dedicated page of the FEHD.
Ends/Friday, September 19, 2025
Issued at HKT 19:40
Issued at HKT 19:40
NNNN