Dengue is a viral infection caused by the Dengue virus. There are 4 species that can infect man. Dengue infection the type of viral Haemorrhagic fevers (viral infections that produce bleeding).
2. How common is dengue infection ?
It is extremely common. As per the data by CDC (Atlanta USA) about 40 crore cases occur each year all around the world.
3. How dangerous is dengue infection ?
Although the number of cases is very high , patients with complications are very few. I would advice patients not to panic just because Dengue is diagnosed.
4. How does Dengue spread ?
Dengue infection is spread by the Aedes aegypti mosquito. How does mosquito get infected? When the mosquito bites a patient infected with Dengue virus, the virus enters the mosquito. The virus then spreads in the body of the mosquito and infects the salivary glands of the mosquito. How does mosquito infect humans? When this mosquito bites another person, the virus from the salivary glands then infect that person. The mosquito once infected remains infected for life (2 weeks) and continues to transmit disease to every person it bites, but dengue virus does no harm to the Aedes mosquito. Dengue cannot spread from one person to another without the Aedes mosquito. You cannot get Dengue by coughing, sneezing, touching or nursing a dengue patient.
5. Where does dengue occur ?
Dengue is very common in the tropical countries where Aedes aegypti mosquito is common.
6. There are many mosquitoes around by building. How can I make out if it is Aedes ?
Besides biological details, common man can identify the species by observing how the mosquito sits on your skin before it bites.
Aedes Mosquito will sit with its tail pointing towards the skin. It also has stripes.
Culex mosquito sits horizontally and has no stripes. It transmits filariasis.
Anopheles mosquito sits with its tail up and transmits malaria.
7. What are the symptoms of Dengue infection ?
Dengue infection typically produces high continuous fever which can last from 3-7 days. Common symptoms are very high fever which may touch 104 F, headaches, vomiting, extreme weakness, severe eye pain, body aches, joint pain, abdominal pain and sometimes rash. The symptoms are not different from those of malaria which is also common in the same areas as dengue.
8. Why is the incidence of Dengue increasing ?
It is because of excess breeding of Aedes mosquito. My personal observation is that Dengue infection typically rises after festivals like Ganpati. Litter thrown on the road like plastic cups are breeding sites for Aedes. Increase in number of cases takes place about 10 days after the festival season and especially so if it is associated with mild rain. Aedes can breed in small collections of fresh stagnant water like old shoes, leftover coconut shells, plastic cups, plant pots tray, tyres, A.C.trays etc. The aedes female mosquito lays eggs after a blood meal. These eggs develop into adult mosquitoes if there is water. In case there is no water they can remain dormant for several months till they come in contact with water. It is very difficult to detect and eliminate mosquito eggs. It takes about 6 days for a adult mosquito to develop from an egg. An adult mosquito will live for 2 weeks. It lays eggs 4 times during its lifetime, about 100 eggs at a time. Aedes mosquito is also showing resistance to pesticides.
9. How can we prevent breeding of Aedes mosquito ?
Aedes mosquito flies only about 100 meters from its breeding site. So if you have a person who is suffering from Dengue we must try and find the breeding spot. Common places are A.C.trays, thrown away cups filled with some water or any other water storage container where water is stagnant, leaking water pipes which leads to collection of water, plant pots. Water collects in the plates kept at the bottom of the pots and Aedes can breed there. A simple remedy like putting salt in the bottom of the plant pot can prevent breeding, as Aedes only breeds in fresh water. Also it is important to clean the water storage devices atleast once every every week and keep it covered. Avoid throwing plastic cups and bottles as a litter.
10. How does Dengue affect the body ?
Dengue virus infects all the cells. However its effect on the cells of the bone marrow is most noticeable. Dengue virus causes maturation arrest of all the cells in the marrow and produces decrease in platelet count (Thrombocytopenia) and decreased WBC count (leucopenia).
11. Which are the tests done to diagnose Dengue ?
a. First 1-4 days of fever : Dengue Antigen , NS1 antigen test is positive.
b. 4 -10 days : Dengue IgM antibody becomes positive. This test may be negative in the first few days.
c. False positive tests due to other infections are also seen. So every positive test does not mean Dengue if not associated with other positive parameters in blood counts.
d. Low platelet counts. Platelet counts can decrease dramatically within a day. During recovery phase they can also increase dramatically in a day or 2.
e. Decrease in White blood cell (WBC) counts also called as leucopenia.
f. Increase in lymphocytes with presence of activated lymphocytes.
12. What are the complications of Dengue ?
a. Bleeding in the skin and internal organs can be seen due to low platelet count. However it is uncommon.
b. Damage to capillaries can produce leakage of water from the blood stream into the lungs producing excess accumulation of water in the lungs (Pulmonary edema). This is the most dangerous complication.
13. Why only some people get complications ? Others don't.
Complication like pulmonary edema are not caused directly by the virus. They are caused by the reaction of the body to the virus. Different people react differently to the virus. So only a few people have complications. If a family suffers from Dengue, it is possible only one person has complications, although the virus is the same.
14. Who is likely to have complications ?
a. Persons who have suffered before are more likely to have complications.
b. Very old, very young and persons with other diseases like asthma, heart ailment, severe diabetes should be more careful.
15. What tests can be done to predict complications ?
There is no sure shot test available. However the following parameters should be done serially.
a. Platelet count : If it drops below 20,000, Immediately consult your physician.
b. If the Hemoglobin rises significantly, it indicates that there is haemoconcentration due to loss of water from the capillaries. This is a sign of complication.
16. What is the treatment of dengue ?
There is no anti viral agent currently available to kill or eliminate the dengue virus. Dengue is a self limiting disease that the immune system cures. Treatment is essentially symptomatic to control fever and body pain and supportive treatment to prevent complications. Platelet transfusion is given in patients who have bleeding.
TAKE HOME MESSAGE
Dengue is a common viral infection that infects thousands of people. Complications are uncommon but unpredictable. All of us must try and keep our surroundings clean so that Aedes mosquito does not breed.