Dengue is a mosquito-borne viral disease. Though the disease takes on an epidemic form almost every year creating panic among the public, dengue is preventable.
Who is the culprit causing Dengue?
The virus is contracted from the bite of a female, striped Aedes aegypti mosquito that has previously bitten an infected person. The mosquito flourishes during rainy seasons but can breed in water-filled flower pots, plastic bags, and cans year-round. One mosquito bite can cause the disease.
The virus is not contagious and cannot be spread directly from person to person. It is mosquito-borne, so there must be a person-to-mosquito-to-another-person pathway. The full life cycle of the virus involves the mosquito as the vector (transmitter) and the human as the source of infection.
What is its breeding pattern?
The female mosquito bites on the elbows and ankles. The female dengue mosquito never sucks a stomach-full of blood at one go but darts from one person to another takes just a sip, until the dengue virus spreads to several people. After every meal, she lays a batch of 400 to 500 eggs, which happens about 5 times in her lifespan. The mosquito lays the eggs in a different place every time. Aedes aegypti lays eggs on the sides of containers and these remain stuck to the surface like glue. The eggs can survive without water for almost a year and hatch as soon as they are submerged in water. The larvae that emerge from the eggs are also tough and can survive in water for a long time even if the temperature is unfavorable. This makes it more important to avoid water stagnation in any form. The dengue mosquito prefers to rest indoors as this protects them from climatic changes thereby increasing their lifespan. Unlike malaria mosquitoes, dengue mosquitos bite during the day with their activity peaking at dawn and dusk. Dengue mosquitoes can’t breed once the temperature falls below 16 degrees. They are generally active between the time period of August-October, which is the peak period for both malaria and dengue.
When do you need to rush to the doctor?
The clinical features of dengue fever vary according to the age of the patient. Individuals should suspect dengue when a high fever (40°C/ 104°F) is accompanied by two of the following symptoms:
- A severe headache
- Pain behind the eyes
- Nausea, Vomiting
- Swollen glands
- Muscle and joint pains
Also known as “break-bone” fever because it sometimes causes severe joint and muscle pain that feels like bones are breaking.
Symptoms usually last for 2-7 days, after an incubation period of 4-10 days after the bite from an infected mosquito.
One should immediately go to the doctor if experiencing symptoms like recurrent vomiting, intolerable severe aches, headache/body ache, high-grade fever, low BP, drowsiness, severe exertion, bleeding from any body part, rapid fall in platelets etc. The period of maximum risk is between the third and the seventh day of illness. But there is no need to panic and no platelet transfusion is required unless platelet count is less than 10,000 or there is a presence of spontaneous bleeding. During epidemics, people of all ages are involved otherwise the disease is more common in children. Presence of restlessness (oxygen deficiency in the brain), abdominal pain and black stools (GI bleeding), minor bleeding from skin, nose, mouth etc signifies urgency. Most dengue infections result in relatively mild illness, but a very small percentage of infections can develop into the far more serious dengue hemorrhagic fever (DHF). This disease is identified with low platelet count, leaking blood vessels causing bleeding from bodily orifices through nose, mouth, and gums. Bruising can be another sign of bleeding inside the body. Unavailability of right treatment at right time can result in the collapse of the blood vessels causing shock (Dengue shock syndrome) and very often death. Thus it is very necessary to seek for urgent medical help if the patient starts bleeding from body orifices. Dengue hemorrhagic fever is a serious condition responsible for 10% of total dengue-related mortality.
How long does dengue fever last?
The acute phase of dengue with fever and muscle pain (myalgia) lasts about one to two weeks. Convalescence is accompanied by a feeling of weakness (asthenia) and fatigue, and full recovery often takes several weeks.
Drinking papaya leaves juice, goat’s milk etc will help in gaining blood platelets?
FALSE. It’s a myth.
How is Dengue Fever diagnosed?
There are four main laboratory methods to diagnose dengue infection: NS1 Antigen, viral isolation in culture, detection of viral RNA by PCR technique, and specific IgM/IgG antibodies in paired sera. The gold standard is usually a combination of dengue NS1 and serology (Antibodies) methods. Dengue NS1 is positive in 80% cases in first day and in 2-3 days it is 60-80% positive. IgM test may take 5-7 days to become positive. Viral isolation is costly, the results are usually available after 6 to 10 days and it is only obtainable in laboratories with the appropriate infrastructure for cell culture or mosquito colonies.
The RT-PCR and other PCR-based techniques give results within 24 hours but they are also costly and they are not available for most clinicians.
On the contrary, there are commercially available immunochromatographic and ELISA tests for the detection of IgM/IgG antibodies which give results within minutes or few hours. However, the detection of antibodies in a dengue-infected person is only possible after 4-5 days of disease onset.
How can it be treated?
There is no specific treatment for dengue fever.
Patients should seek medical advice, rest and drink plenty of fluids. Paracetamol can be taken to bring down fever and reduce joint pains. However, aspirin or ibuprofen should not be taken since they can increase the risk of bleeding.
For severe dengue, medical care by physicians and nurses experienced with the effects and progression of the disease can frequently save lives. Maintenance of the patient’s circulating fluid volume is the central feature of such care.
Not to worry! Dengue Fever can be prevented!
The World Health Organization recommends an Integrated Vector Control program
Preventing or reducing dengue virus transmission depends entirely on controlling the mosquito vectors or interruption of human-vector contact. WHO promotes the strategic approach known as Integrated Vector Management (IVM) to control mosquito vectors, including those of dengue.
Methods of vector control
Ae. Egypt uses a wide range of confined larval habitats, both man-made and natural.
Some man-made container habitats produce large numbers of adult mosquitoes, whereas others are less productive. Consequently, control efforts should target the habitats that are most productive and hence epidemiologically more important rather than all types of container, especially when there are major resource constraints.
Vector transmission is reduced through the use or combination of these three methods:
- Environmental management
- Chemical control
- Biological control
Individual and household protection
Clothing that minimizes skin exposure during daylight hours when mosquitoes are most active affords some protection from the bites of dengue vectors and is encouraged particularly during outbreaks.
Repellents may be applied to the exposed skin or to clothing. The use of repellents must be in strict accordance with label instructions.
Insecticide-treated mosquito nets afford good protection for those who sleep during the day (e.g. infants, the bedridden and night-shift workers).
Where indoor biting occurs, household insecticide aerosol products, mosquito coils or other insecticide vaporizers may also reduce biting activity.
Household fixtures such as window and door screens and air-conditioning can also reduce biting.
Safe use of insecticides
All pesticides are toxic to some degree. Safety precautions for their use – including care in the handling of pesticides, safe work practices for those who apply them, and appropriate field application – should be followed.
WHO Pesticide Evaluation Scheme (WHOPES) has published specific guidelines on the use of insecticides, safety procedures, quality control and guidelines for testing.
New and novel methods to combat dengue are being researched upon every day.
Sanofi’s vaccine, Dengvaxia which is designed to coax the body’s immune system into making antibodies against all four forms of dengue, is a live virus comprised of an attenuated yellow fever virus. (Yellow fever virus and dengue virus have the same genus.) For the vaccine, however, the virus is genetically engineered to include genes encoding for dengue proteins.
Some other examples include the release of sterile male mosquitoes and a promising method which involves infecting the mosquito with a harmless natural bacterium called Wolbachia. This bacterium blocks the dengue virus from growing in the mosquito’s body.