DH urges public to work together to step up mosquito control and prevention measures amid global spread of mosquito-borne diseases
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"Although there have been no new imported cases of CF in the past six consecutive days, high temperatures and rainfall levels continue to pose a risk of outbreaks of various mosquito-borne diseases in Hong Kong and around the world. Members of the public must remain vigilant and take proper mosquito control and personal protective measures both locally and during travel. Individuals experiencing relevant symptoms should seek medical advice promptly and inform their doctors if they have travel history," the Controller of the CHP, Dr Edwin Tsui said.
"As the new school year is about to begin, the CHP also urges educational institutions to follow the Food and Environmental Hygiene Department (FEHD)'s anti-mosquito guidelines to strengthen efforts to clear stagnant water on school premises and eliminate mosquito breeding sites. Through the Education Bureau, the CHP will once again remind schools, staff and students to prevent the spread of mosquito-borne diseases on campus. While mosquito-borne diseases are not transmitted from person to person, but it requires the collective effort of the entire community to eliminate mosquito breeding sites in order to effectively prevent such diseases and protect one's own health and one's family members," Dr Tsui added.
The following is the latest situation and relevant health information on major mosquito-borne diseases in Hong Kong and worldwide:
1. CF
Hong Kong has recorded nine imported CF cases this year, involving six males and three females aged between 8 and 79 years. Five cases involved individuals who had travelled to Foshan in Guangdong Province during the incubation periods, while four involved individuals who had travelled to Bangladesh. Three patients developed symptoms before returning to Hong Kong and the remaining six patients developed symptoms between the first and the fifth day after returning. Regarding symptoms, all patients experienced fever, and the vast majority (eight cases) reported joint pain, which typically appeared on the same day or the day after the onset of fever. The most commonly affected body parts were the wrists, elbows, knees and ankles.
The public should be aware that, in addition to Foshan in Guangdong Province, many countries worldwide are currently experiencing outbreaks of CF. Before travelling aboard, it is essential to pay attention to the situation of the destinations, and take mosquito prevention and personal protection measures. After returning to Hong Kong from affected areas, it is also necessary to continue monitoring one's health condition.
2. Dengue Fever (DF)
No DF cases were recorded in Hong Kong between August 15 and 20. There have been 41 imported DF cases recorded so far this year. Although the figure is slightly lower than the same period last year, the DF situation remains severe in Hong Kong's neighbouring regions and worldwide. Hence, the risk of continual occurrence of imported cases is still high.
According to the World Health Organization (WHO), the global incidence of DF has markedly increased over the past two decades. In 2024, over 14 million cases were recorded, setting a new record high. Indonesia, Malaysia, Thailand and Vietnam have each recorded over 20 000 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 a total of 586 locally infected cases so far this year, with relatively more cases in Guangzhou, Foshan, Chaozhou and Shenzhen.
DF is also transmitted to humans through the bite of female Aedes mosquitoes carrying the DF virus. Symptoms are similar to those of CF, including high fever, headache, pain behind the eyes, muscle and joint pain, and rash. The incubation period is usually four to seven days. Dengue haemorrhagic fever (DHF) is a severe form of DF with increased bleeding tendency; the mortality rate can be as high as 20 per cent. Patients who have a second infection with a different serotype of DF virus are more likely to result in DHF.
3. Japanese encephalitis (JE)
The CHP yesterday announced an imported case of JE, marking the first such case recorded in Hong Kong since 2020. The primary vector of JE is the Culex tritaeniorhynchus. Mosquitoes breed in areas where there is a lot of stagnant water, such as rice paddies, and become infected when they bite pigs or wild birds infected with the JE virus. The infected mosquitoes then transmit the virus to humans and animals during biting. JE is prevalent in rural areas of Asia and the Western Pacific Region, especially in hot season. In the subtropics and tropics, transmission can occur year-round, often with a peak during the rainy season.
The incubation period from infection to onset of symptoms is four to 14 days. Most patients with JE have mild symptoms, with no significant symptoms other than fever and headache. However, approximately one in every 250 infections is associated with severe illnesses characterised by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis, and even death.
4. Zika virus
No infection case of Zika virus had been recorded in Hong Kong this year. However, there were two and three imported cases recorded in 2023 and 2024 respectively, involving patients who had visited India and Thailand during incubation period. Surveillance data revealed that a relatively higher number of infection case of Zika virus have been recorded in the Southeast Asia, India and the Americas.
Aedes aegypti, which is the primary vector for Zika virus, is currently not found in Hong Kong, but other Aedes mosquito species (such as Aedes albopictus) are also considered as potential vectors. Symptoms of Zika including rash, fever, conjunctivitis, headache, muscle and joint pain, but most people infected with Zika Virus are asymptomatic. Zika virus infection during pregnancy is a cause of microcephaly and other congenital malformations in infants. Thus, pregnant women should pay close attention to the infection risk and adopt precautions against mosquito-borne diseases if they travel to affected areas.
To raise awareness among the elderly about preventing mosquito-borne diseases, the Visiting Health Teams under the Elderly Health Service of the DH have been advising the elderly on mosquito-borne diseases prevention and tips on travel health at health talks conducted at District Elderly Community Centres and Neighbourhood Elderly Centres. Besides, the Visiting Health Teams have also reminded all residential care homes for the elderly in Hong Kong to enhance mosquito control measures. The DH's Maternal and Child Health Centres, Student Health Service Centres and Special Assessment Centres also advise pregnant women, infant carers and students on symptoms and preventive measures of the mosquito-borne diseases.
Avoiding mosquito bites and eliminating mosquito breeding sites are effective ways to prevent mosquito-borne diseases. Aedes albopictus, which is the vector for CF, DF and Zika virus, is common in Hong Kong, and Culex tritaeniorhynchus, the primary vector for JE, can also be found in Hong Kong. Members of the public should maintain strict environmental hygiene, mosquito control and personal protective measures both locally and when travelling outside Hong Kong.
Members of the public returning to Hong Kong from areas affected by mosquito-borne diseases should continue to apply insect repellent and monitor their personal health condition. If they feel unwell, they should seek medical attention immediately and inform their doctors of their travel history. The public should avoid using non-steroidal anti-inflammatory drugs (such as ibuprofen), to prevent aggravating the risk of haemorrhage. In general, children should not take medications containing aspirin to relieve fever or other symptoms because it may lead to Reye's syndrome, a serious and potentially fatal complication.
Members of the public may visit the following pages for more information on mosquito prevention and control: 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/Thursday, August 21, 2025
Issued at HKT 20:12
Issued at HKT 20:12
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