With a dengue epidemic descending on Singapore, Jasmine Chung finds out more about the disease and what can be done to prevent its proliferation.
The World Health Organization (WHO) estimates that there are 50 to 100 million dengue infections worldwide. In Singapore, approximately 10,000 dengue cases have been reported in the first half of this year, with a record high of 820 cases over a single week in June. There have already been four confirmed deaths due to dengue this year.
What is Dengue Fever?
Dengue fever is caused by a viral infection transmitted through the bite of two mosquito species: the Aedes aegypti and Aedes albopictus.
Symptoms include sudden-onset fever, headaches, muscle and joint pains, and a skin rash similar to measles. While the majority of dengue infections involve mild symptoms akin to the common cold, some people suffer so severely that it’s considered life-threatening.
Most dengue infections are mistaken for simple viral fever. Two severe but rare forms are dengue haemorrhagic fever (which results in bleeding, declining levels of blood platelets or blood plasma leakage) and dengue shock syndrome (when extremely low blood pressure occurs).
The incubation period (time between being bitten by a mosquito and when symptoms manifest) is four to seven days. Dengue is usually self-limiting; the illness resolves itself without medical intervention, usually within one to two weeks. Hospitalisation is not always necessary: patients may be kept for observation, then given medication and fluids, before resting at home. Only on a second visit with continued or worsened symptoms will more tests and diagnosis tools (blood tests, X-rays, etc) be ordered.
As there is neither vaccine nor drug that works against dengue, treatment is therefore conservative, with bed rest, fluids and analgesics such as paracetamol to manage the pain.
There are four distinct serotypes or strains of the dengue virus: DEN1 to DEN4. Recovery from one strain provides lifelong immunity against that particular serotype, while cross-immunity to the other three after recovery is only partial and temporary (up to a few months).
Researchers have noticed that a person reinfected by another serotype has a higher risk of developing severe symptoms. “[These people] may have a different immune response wherein the clinical symptoms of dengue might worsen and the person will have severe disease,” says E Sreekumar, virology expert at the Rajiv Gandhi Centre for Biotechnology in Kerala, India.
Even with immunity against the same dengue strain, it is still possible to develop a fever while the body fights against the infection.
Prevention is Better than Cure
To prevent dengue fever, we must reduce the frequency of mosquito bites by breaking the breeding cycle of the dengue carrier, the Aedes mosquito, identifiable by the distinctive black and white stripes on its body. We can get rid of them by frequently checking and removing stagnant water at home.
The National Environment Agency oversees the surveillance of the vector population by actively monitoring the formation of dengue clusters island-wide and carrying out ultra-low volume (ULV) misting. They will be distributing insect repellent to households in the major cluster areas from July to August.
However, the risk of dengue transmission is elevated by our tropical climate. As the majority of breeding spots are in homes, especially in dark or shady corners, and in clean and stagnant waters, we have to do our part to prevent the breeding of this silent killer.
The Aedes mosquito is not the exclusive carrier of the dengue virus. Infected humans are also carriers for up to one week from the time they first got the virus. A dengue-free mosquito that feeds on an infected human will then carry the virus and infect the next victim it feeds on.
While we may be able to prevent mosquitoes from breeding in our homes, we may not be able to prevent them from flying into our houses or biting us while we are outdoors. See sidebar for tips on how to avoid getting bitten by mosquitoes. Dr Leong Hoe Nam, Infectious Diseases Physician at Rophi Clinic, advises, “If a person falls ill with fever, assume that it’s dengue. And I would drink lots of water; the key to breaking the dengue fever and getting out of it alive is getting enough water.”
Physician Lin Xiao Yan, who is based in the Tiong Bahru and Hougang branches of Eu Yan Sang Traditional Chinese Medicine (TCM) Clinic, recalls a case of a married couple from Hougang who were both infected with dengue at the same time. While the wife presented mild symptoms and was advised to rest at home, the husband had it much worse, and required a blood transfusion in a hospital.
“To a TCM physician, dengue fever belongs to the category of warm diseases,” explains Physician Lin. “Treatment methods include getting rid of warm pathogens and tackling the disease via prevention, qi, nutrition and blood.”
The categories of warm diseases are as follows:
The Surface (Wei) Stage
Symptoms: fever, diminished perspiration, headache, redness on edges and tip of tongue, rapid floating pulse, thin white coating on tongue
Commonly used herbs: honeysuckle, platycodon root, weeping forsythia, lophatherum herb, peppermint, kudzu root
The Qi Stage
Symptoms: high fever, profuse perspiration, dry mouth with craving for cold beverages, dark-coloured urine, dark red tongue, yellow tongue coating
Commonly used herbs: gypsum, anemarrhena, raw licorice root, baikal skullcap root, ophiopogon, cape jasmine
The Nutritive (Ying) Stage
Symptoms: fever that’s aggravated at night, insomnia, light spotting on skin, dark red tongue, thready pulse
Commonly used herbs: raw rehmania root, ophiopogon, salvia root, gentian root, honeysuckle, weeping forsythia
The Blood Stage
Symptoms: high fever, restlessness, spotting and rashes, blood in vomit, urine and stool
Commonly used herbs: raw rehmania root, peony bark, white peony root, cape jasmine, comfrey, lalang grass rhizome
Tips to Repel Mosquitoes
- Use natural repellents such as citronella oil, lemon eucalyptus oil, or even vanilla.
- Dress in protective clothing (long-sleeved shirts, long pants, socks, shoes), especially at dawn and dusk.
- Keep unscreened windows and doors closed.
- Grow these plants at home to ward off mosquitoes: orange jasmine, venus fly trap, Spanish flag, night-blooming cestrum, citronella mosquito plant, mint, jessamine, pyrethrum
Photo courtesy of Shutterstock. This article first appeared in NATURA magazine issue No.6.