Last updated on 24 January 2022
What is dengue fever?
Dengue fever is a mosquito-borne viral infection that continues to rapidly spread worldwide. It’s known to cause a wide spectrum of disease, ranging from an infection that is nearly or completely asymptomatic to severe flu-like symptoms. In less common cases, some people may develop severe dengue, which can be fatal when not managed appropriately.
Dengue is common in 129 countries, particularly in Asia where the tropical and sub-tropical climates are fertile grounds for the Aedes mosquito – the chief transmitter of the disease. According to the World Health Organisation, there are an estimated 100 – 400 million infections each year. As of late, Singapore has seen a steadily increasing number of dengue cases. In fact, the National Environment Agency warns of an increased risk of dengue cases in the warmer months ahead.
Dengue fever: Symptoms and signs
Dengue symptoms usually begin 4 – 6 days after infection and can last up to 10 days. Symptoms can range from mild to severe. The symptoms can be confused with other illnesses that cause fever, aches, pains, and rashes.
The most common symptoms of dengue are as follows:
- Sudden, high fever
- Skin rash (which may appear 2 – 5 days after the onset of fever)
- Severe headaches
- Backaches and severe body aches
There are also warning signs to watch out for which may indicate you have severe dengue. These warning signs generally begin 24 – 48 hours after the fever goes away. Severe dengue can be life-threatening within a few hours and typically require hospitalisation:
- Pain or tenderness in the stomach or abdomen
- Repeated vomiting with dehydration
- Vomiting blood or presence of blood in stools
- Feeling tired, restless, or irritable
- Low platelets with bleeding in stomach, joint, muscle, gums, nose and brain (dengue haemorrhage fever)
- Hypotension/drop in blood pressure (dengue shock syndrome)
- Giddiness and fainting spells
10 facts about dengue
Considering the worldwide prevalence of dengue, it’s imperative that you arm yourself with important facts relating to this viral disease. These are 10 things that you need to know about dengue to help you gear up against the disease:
1. Dengue fever is most common in sub-tropical and tropical areas
Dengue outbreaks occur in several countries, including the Americas, Africa, the Middle East, Asia, and the Pacific Islands. In fact, the only continent not affected by dengue is Antarctica.
Dengue outbreaks can occur anytime and anywhere as long as warm weather conditions favour mosquito survival and the mosquitoes are active.
The greatest risk for dengue occurs in the following areas which are known to have sub-tropical and tropical climates:
- Southeast Asia
- Southern China
- Indian subcontinent
- The Pacific Islands
- The Caribbean (except Cuba and the Cayman Islands)
- Central and South America (except Chile, Paraguay, and Argentina)
2. Dengue is spread by a specific species of mosquito
Dengue is transmitted through the bite of the Aedes mosquito infected with a dengue virus. The Aedes aegypti mosquito is the main vector that causes dengue. However, dengue outbreaks have also been attributed to Aedes albopictus, Aedes polynesiensis, and several species of the Aedes scutellaris complex. The Aedes aegypti is most active during the day. They tend to bite approximately 2 hours after sunrise and in the evening before the sun sets.
3. Aedes mosquitoes breed in stagnant water
Mosquitoes thrive in urban areas close to human population. They prefer to breed in clean, stagnant water that is easily found in the household. All it takes is a very small amount of water for mosquitoes to lay their eggs. Examples where stagnant water can be found include water bottles, containers, discarded waste, or anything that is capable of holding water. Inside the home, adult mosquitoes can be found in dark areas such as closets, under beds, and behind curtains where they are protected from wind, rain, and potential predators.
4. Dengue is transmitted in different ways
There are a couple of ways that dengue is transmitted. The first is mosquito-to-human, in which an infected Aedes mosquito bites a human, effectively spreading the dengue virus. Mosquitoes, in turn, can become infected when they bite a person infected with the virus. These infected mosquitoes can then spread the virus to other people through bites.
The dengue virus can also be transmitted from pregnant mother-to-child. A pregnant woman already infected with dengue can pass on the virus to her foetus during pregnancy.
5. You can get the dengue virus more than once
It is possible that you can get the dengue virus more than once. The virus responsible for causing dengue is called dengue virus (DENV). There are 4 DENV serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), which means it is possible to be infected 4 times. While recovery from infection is believed to provide lifelong immunity against that serotype, cross-immunity to the other stereotypes is only partial and temporary. It’s also important to note that a second infection carries a higher risk of developing severe dengue which can be fatal.
6. Dengue is diagnosed through a blood test
Diagnosing dengue fever can be difficult, because its signs and symptoms can be easily confused with those of other diseases such as malaria, leptospirosis, and typhoid fever. As part of diagnosing your illness, your doctor may ask you about your medical and travel history. Be sure to let your doctor know of international trips and travel dates. Doctors can also diagnose dengue infection with a blood test to check for the virus or antibodies to it. They may also order blood tests for similar viruses such as zika or chikungunya.
7. Dengue is preventable, but a cure has not yet been developed
There is currently no specific medicine to treat dengue. If you suspect you have dengue fever, you may manage symptoms such as fever, muscle aches and pains with medication containing acetaminophen or paracetamol. It’s also imperative that you get plenty of rest, drink lots of fluids, and see a doctor immediately.
8. Medication to avoid when suffering from dengue
There is medication that needs to be avoided when you’re stricken by dengue. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin should be avoided because they thin the blood. As dengue can cause risk of haemorrhage, NSAIDs may increase bleeding risk and worsen the condition.
9. Dengue can be easily prevented
Making a few home and lifestyle adjustments can help prevent dengue, as all four dengue virus serotypes are spread primarily through the bite of an infected mosquito.
Tips to prevent dengue:
- Apply mosquito repellent, even at home
- Spray insecticide in dark corners of your home, including under the bed, behind the sofa, and behind curtains
- Wear long-sleeved shirts and trousers when outdoors
- Consider air conditioning at home, if available
- Ensure that all windows and door screens are secure and free of holes
- Use mosquito nets if sleeping areas are not screened
- Get rid of stagnant water at home and change water in vases/bowls on alternate days
10. Dengue can be fatal when left untreated
While many dengue infections are mild, it can cause acute flu-like illness which can develop into severe dengue. Severe dengue, also known as dengue shock syndrome (DSS), is a potentially lethal complication and will require hospitalisation and management by medical professionals. Dengue shock symptoms occur after 2 – 6 days if the patient remains untreated.
Dengue shock syndrome symptoms include:
- Cold/clammy hands and feet
- A weak pulse
- Blueness around the mouth
Without proper treatment, the mortality rate for severe dengue increases to 20%. There is a vaccine (Dengvaxia®) available for people who have been infected by dengue before. The course of the vaccination consists of 3 injections, spaced out over the course of a year. Most clinics offer the vaccine, but do consult your doctor before taking the vaccination.
If you are experiencing any of the severe dengue symptoms mentioned above, seek medical attention immediately at your nearest clinic or accident & emergency department.
Article reviewed by Dr Jim Teo, respiratory physician and intensivist at Parkway East Hospital
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