BY DR. ASHWANI KUMAR

The incidence of dengue is rapidly increasing in the state. The disease can only be prevented with sustainable, community-based, integrated mosquito control, with limited reliance on insecticides.

DENGUE (Pronounced den’gee) is a disease caused by any one of four closely related viruses (DEN-1, DEN-2, DEN-3, or DEN-4). The viruses are transmitted to humans by the bite of an infected mosquito (Aedes aegypti). The Aedes aegypti mosquito is the vector for dengue/DHF (Dengue Hemorrhagic Fever). It is estimated that there are over 100 million cases of dengue worldwide each year. This disease is now endemic in most tropical countries. The last few years have shown unusually high rates of dengue cases in the South East Asia region, and doctors are worried that global warming may be partially to blame. The geographical distribution has greatly expanded over the last 30 years because of increased potential for breeding of Aedes aegypti, the vector species. This has been prompted by demographic explosion, rapid growth of urban centres with a strain on public services, such as potable water. Dengue has emerged as a major public health problem of international concern.

As per current estimates, at least 100 countries are endemic for DHF and about 40% of the world population (2.5 billion people) are at risk in tropics and sub-tropics. According to estimates, over 50 million infections with about 400,000 cases of DHF are reported annually, which is a leading cause of childhood mortality in several Asian countries.

DHF is a more severe form of dengue. It tends to affect children under ten, causing abdominal pain, haemorrhage (bleeding) and circulatory collapse (shock). It can be fatal if unrecognised and not properly treated. DHF is caused by infection with the same viruses that cause dengue. With proper management, mortality due to DHF can be reduced.

TRANSMISSION

DENGUE is transmitted to people by the bite of an Aedes mosquito that is infected with the dengue virus. The mosquito becomes infected with dengue virus when it bites a person who has dengue or DHF and, after about a week, can transmit the virus while biting a healthy person. Dengue cannot be spread from person to person.

Outbreaks of dengue occur primarily in areas where Aedes aegypti (sometimes also Aedes albopictus) mosquitoes are found in large numbers. The mosquito breeds in containers, empty coconut shells, tyres, etc. This includes urban areas as well as rural areas. Dengue viruses may be introduced into areas by migratory workers who become infected while visiting other endemic areas, where dengue commonly exists. The transmission is year-round, but the rainy season increases mosquito breeding.

Signs & Symptoms. The principal symptoms of dengue are high fever, severe headache, backache, joint pains, nausea and vomiting, eye pain and rash. Generally, younger children are more affected than older children and adults.

Dengue hemorrhagic fever is characterised by a fever that lasts from 2-7 days, with general signs and symptoms that could occur with many other illnesses (e.g., nausea, vomiting, abdominal pain and headache). This stage is followed by haemorrhagic manifestations, tendency to bruise easily or other types of skin haemorrhages, bleeding nose or gums, and possibly internal bleeding. The smallest blood vessels (capillaries) become excessively permeable (‘leaky’), allowing the fluid component to escape from blood vessels. This may lead to failure of the circulatory system and shock, followed by death, if circulatory failure is not corrected.

Dengue Shock Syndrome (DSS). All the above criteria of DHF plus signs of circulatory failure are diagnosed as DSS. The patient will have a rapid and weak pulse, narrow pulse pressure (< or equal to 20 mm Hg), hypotension, cold and clammy skin and restlessness.

The above descriptions of DF/DHF/DSS are adequate to guide doctors to treat the disease. However, for reporting of the disease, cases should be classified as suspected DF/DHF/DSS on the basis of the above criteria. Added serological evidence would categorise them into probable and confirmed cases.

If you or any family member is suffering from suspected dengue fever, it is important to carefully watch yourself or relative for the next few days, since this disease can rapidly become very serious and lead to a medical emergency. The complications associated with Dengue Fever/Dengue Haemorrhagic Fever usually appear between the third and fifth day of illness. You should therefore watch the patient for two days even after fever disappears.

The patient should take complete rest. Immediately consult a doctor if any of the following manifestations appear:

Red spots or points on the skin, bleeding from the nose or gums, frequent vomiting, vomiting with blood, black stool, sleepiness, constant crying, abdominal pain, excessive thirst (dry mouth), pale, cold or clammy skin, difficulty in breathing

Do not wait in case the above symptoms appear. Immediately consult a doctor. It is crucial to quickly get treatment in case of these complications.

TREATMENT

THERE is no specific medication for treatment of a dengue infection. Persons who think they have dengue should use analgesics (pain relievers) with paracetamol and avoid those containing aspirin, ibuprofen. They should also rest, drink plenty of fluids (water, soup, milk, juice), and consult a physician.

As with dengue, there is no specific medication for DHF. It can, however, be effectively treated by fluid replacement therapy if an early clinical diagnosis is made. Hospitalisation is frequently required in order to adequately manage DHF.

Prevention. There is no vaccine for preventing dengue. The best preventive measure for residents living in areas infested with Aedes aegypti is to eliminate the places where the mosquito lays her eggs, primarily artificial containers that hold water.

Items that collect rainwater or are used to store water (for example, plastic containers, drums, buckets, or used automobile tires) should be covered or properly discarded. Pet and animal watering containers and vases with fresh flowers should be emptied and scrub dried at least once a week. This will eliminate the mosquito eggs and larvae and reduce the number of mosquitoes present in these areas.

For travellers to areas with dengue, as well as people living in areas with dengue, the risk of being bitten by mosquitoes indoors is reduced by windows and doors that are screened. Proper application of mosquito repellents on exposed skin and use of full sleeve clothes decreases the risk of being bitten by mosquitoes.

The emphasis for dengue prevention is on sustainable, community-based, integrated mosquito control, with limited reliance on insecticides (chemical larvicides and adulticides). Preventing epidemic disease requires a coordinated community effort to increase awareness about how to control the mosquito that transmits it. There is a need for effective disease and vector surveillance system based on reliable laboratory and health information systems.

Residents should be made responsible for keeping houses and surroundings free from mosquito breeding by emptying and scrub drying the rotate containers once a week. There is a need for local bodies and NGOs to work hand in hand with community and inter-sectoral participation. There is a need to undertake activities to achieve sustainable behavioural changes and partnerships.

The writer is Joint Secretary of the Voluntary Health Association of Goa.