There are 4 distinct, but closely related, serotypes of the virus that cause dengue (DEN-1, DEN-2, DEN-3 and DEN-4). Recovery from one type of dengue infection provides lifelong immunity against that particular serotype. But subsequent infections by other serotypes increase the risk of developing severe dengue (Haemorrhagic Fever).
Aedes aegypti (Primary vector for Dengue fever)
- The Dengue mosquito lives in domestic habitats and breeds in clean fresh water in man-made containers such as buckets, tyres, bottles, tins, roof gutters, rainwater tanks, wells and natural containers such as palm fronds and tree holes.
- The Dengue mosquito does not breed in ground pools, swamps or dirty storm water drains.
- It is rarely found more than 50 meters from human habitation.
- They like to rest in dark, protected indoor places such as under tables, in closets, behind curtains, etc.
- Only the female mosquito bites humans and therefore transmits the virus.
- The Dengue mosquito is a day-time feeder; its peak biting periods are early in the morning and in the evening before dusk.
- Female bites multiple people during each feeding period.
- The mosquito becomes infected when it feeds on a person who already has the dengue virus.
- Once infected, the virus multiplies inside the mosquito and can infect other people when the mosquito feeds again.
Prevention and Control
At present, the only method to control or prevent the transmission of dengue virus is to focus on the Dengue mosquitoes through:
- Removing containers and disposing of unwanted rubbish around the yard that may collect water e.g. plastic sheets, tarpaulins, wheelbarrows, tyres, foam boxes, etc.
- Avoid using saucers or drip trays under pot plants, let pots drain directly onto the ground.
- Empty bird baths and pet drinking water containers at least weekly and wipe clean.
- Store containers that may collect water upside down and undercover.
- Ensure rain water tanks are appropriately maintained and screened to prevent access for breeding.
- Use of personal household protection such as window screens, mosquito nets, long-sleeved clothes, insecticide treated materials, coils and vaporizers, surface spray.
- Improving community participation and awareness for sustained mosquito control.
- Applying insecticides during outbreaks as one of the primary control measures.
- Active monitoring and surveillance of Dengue mosquitoes to determine effectiveness of control interventions.
Travellers to countries were Dengue Fever is present should stay in accommodation with screened windows and doors. Wear loose fitting clothing that covers the arms and legs and apply insect repellent containing DEET or Picaridin to exposed skin.
- A person infected by the dengue virus develops severe flu-like symptoms.
- Also known as ‘break-bone’ fever, it affects infants, children and adults.
- People with dengue fever begin to develop illness between 3 and 14 days (usually 4-7 days) after being bitten by an infectious mosquito.
- Common symptoms include sudden fever, chills, severe headache with pain behind the eyes, swollen glands, muscle and joint pain and extreme fatigue.
- Additional symptoms include abdominal pain, nausea, vomiting and a red rash (generally on the upper body).
- Fever typically lasts around 6 days.
Severe dengue (Haemorrhagic Fever) is a rare but potentially deadly complication due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. The warning signs to look out for occur 3-7 days after the first symptoms in conjunction with a drop in fever temperature (below 38°C) include:
- Severe abdominal pain
- Persistent vomiting
- Rapid breathing
- Bleeding gums
- Blood in vomit
- Fatigue, restlessness
The next 24-48 hours of the critical stage can be lethal; proper medical care is needed to avoid complications and risk of death.