Aedes albopictus (Acknowledgement: Pest Control Advisory Section, Food and Environmental Hygiene Department)

What is Dengue fever?

Dengue Fever is an acute viral disease characterized by sudden onset of fever for 3-5 days, with intense headache, joint and muscle pain, pain behind the eyes, nausea, gastrointestinal disturbances and rash. Minor bleeding, such as gum and nose bleeding, may occur at any time during the febrile phase. Children usually have a milder disease than adults. The incubation period is 3 to 14 days. Recovery may be followed by prolonged fatigue and depression. Occasionally, the disease may progress to Dengue Heamorrhagic Fever (DHF) with bleeding and shock, leading to death. Travellers to tropical countries, especially in Southeast Asia and Latin America, may be at risk of dengue infection. Epidemics usually occur during and shortly after the rainy season.

How does it spread?

Dengue virus is transmitted to human by mosquitoes, especially Aedes aegypti and Aedes albopictus. This is a day-biting species with increased biting activities for 2 hours after sunrise and several hours before sunset. Patients are usually infective for mosquitoes from shortly before to the end of the febrile period, an average of about 6-7 days. It cannot be directly transmitted from person to person.

How can you prevent it?

At present, there is no effective vaccine for dengue, so travellers must rely on preventing mosquito bites to combat infection (especially during their high biting activity time). The personal protection measures against mosquito bites are as follows:

• Wear long-sleeved shirts and trousers;
  
  
• Rest in air-conditioned or well-screened rooms;
  
  
• Use aerosol insecticide indoor and use bednets if sleeping areas are not air-conditioned or screened.
  
  
• Use insect repellents containing DEET (for children keep DEET concentration below 20%) on exposed skin;
  
  
• If travelling in endemic rural areas, carry a portable bed-net and apply permethrin on it as well as to clothes.
  

How is it treated?

Anyone returning from travel to a dengue-infected area and then falling sick within one month, especially with bleeding signs, should seek medical assistance immediately. High fever should be treated by sponging and the appropriate use of paracetamol. Do not take aspirin because they can lead to bleeding and cause stomach irritation. There is no specific treatment available for treating DHF. Supportive measures have to be provided in hospital.