Dengue Fever
Symptoms, Prevention and Treatment
-Dr. Arvind Singh
Dengue fever is also known as ‘breakbone fever’ is an infectious disease spread by the biting of mosquitoes. It has emerged as a serious health problem in tropical and sub-tropical regions of the world. Dengue is an example of Neglected Tropical Disease.
Dengue fever is a severe, flu-like illness that affects infants, young children, and adults. Dengue has been reported since the 18th century, however, it has become a global problem since the Second World War and is endemic in more than 110 countries. Dengue hemorrhagic fever (DHF) is a potentially lethal complication, characterized by high fever, hemorrhagic phenomena often with enlargement of the liver and in severe cases, circulatory failure.
According to the World Health Organization, there are about 50 million cases of dengue infection worldwide every year with 500,000 cases of Dengue hemorrhagic fever. It is estimated that there are 22,000 deaths annually among children. According to an estimate, nearly 3.97 billion people are at risk of the disease in 128 countries.
The main areas affected by dengue disease include the Caribbean, South and Central America, Mexico, Africa, the Pacific islands, South East Asia, Indian sub-continent, Hawaii and Australia. In India, the disease is mainly confined to urban areas.
The highest burden of disease occurs in South East Asia and the Western Pacific. However, over the last few years, there has been a rising trend in South America and the Caribbean. Dengue cases have also been reported outside tropical and sub-tropical regions. The continued increase in urbanization, population growth, and global travel introduces the virus into new populations.
Transmission:
Dengue fever is caused by an Arthropod-borne virus of the genus Flavivirus within the family Flaviviridae. There are four distinct types of dengue viruses known as DENV-1, DENV-2, DENV-3, and DENV-4. These four are the serotypes of the virus. Serotypes are a group of closely related microorganisms distinguished by a characteristic set of antigens. Infection with one type of virus gives lifelong immunity to that type but only short term immunity to others.
Dengue virus is transmitted by several species of mosquito within genus Aedes, especially Aedes aegypti. Other Aedes species that transmit the disease include Aedes albopictus, Aedes scutellaris, Aedes polynesiensis, and Aedes pseudoscutallaris. The main vector Aedes aegypti is found worldwide between latitudes 35ͦN and 35ͦ S.
Aedes mosquitoes typically live indoors and are often found in dark, cool places such as in closets, under beds, behind curtains and in bathrooms. Human beings are the primary host of the dengue virus but it also circulates in non-human primates. The mosquito becomes infectious 8-10 days after feeding and remain infectious for life.
Dengue can also be transmitted via infected blood products and through organ donation. The disease is also transmitted from mother to child during pregnancy or at birth.
Dengue Fever Symptoms:
Symptoms of the disease appear 3-14 days after the infective bite. The dengue is marked by fever, headache, muscle and joint pains, swollen glands and a characteristic skin rash that is similar to measles. In severe cases the disease develops into fatal dengue hemorrhagic fever, resulting in bleeding, decrease in blood platelets count and blood plasma leakage, or into ‘dengue shock syndrome’, where dangerously low blood pressure occurs.
Evidence of hemorrhage in the body is the chief symptom of dengue hemorrhagic fever. Petechiae (small red or purple blisters under the skin), bleeding in the nose or gums, black stools, or easy bruising are all possible signs of hemorrhage.
What are Blood Platelets?
Blood platelets also called thrombocytes are non-nucleated, round or oval biconvex disc-like bodies. Their number normally varies from 0.15 to 0.45 million per microliter of blood. Blood platelets are formed in the bone marrow. Their life-span is about a week. When a blood vessel is injured, platelets get clumped at the injured spot and release certain chemicals called Platelet Factors which promote coagulation of blood.
Dengue Fever Diagnosis:
Dengue is diagnosed on the basis of symptoms and physical examination. Diagnosis is based on the findings of fever along with two of the following: nausea and vomiting, rash, generalized pains, reduced white blood cell count, positive tourniquet test. The latter involves the application of a blood pressure cuff for five minutes, followed by the counting of any petechial hemorrhages. A higher number makes a diagnosis of dengue more likely.
Dengue Fever Treatment:
Since dengue fever is a viral disease hence there is no specific medicine or antibiotic to treat it. Even there is no vaccine available against the disease. A person suffering from dengue fever is asked to take plenty of fluid. Moreover, an antipyretic drug-like Paracetamol is used to calm down the fever. Blood platelet transfusion is done in serious cases of dengue fever.
Control of Dengue:
The bite of one infected mosquito can cause infection. The risk of being bitten is highest during the early morning, several hours after daybreak, and in the late afternoon before sunset. However, mosquitoes may feed at any time during the day.
The control of dengue requires the eradication of the mosquitoes which carry the virus that cause dengue. Since Aedes aegypti, the principal vector of the disease breeds in the clean water hence water logging in the form of small pools should be avoided in the surroundings. There should be regular use of insecticides to keep the mosquito population at bay. Mosquito repellant ointments/creams and mosquito nets should be used to avoid the mosquito bite.
Conclusion:
It can be concluded that dengue fever is a serious health problem in tropical and sub-tropical regions of the world causing large scale mortality every year. Since the disease has no specific treatment hence effective prevention is the only way to avoid the chances of infection. Prevention should be by minimizing mosquito bites, especially during the daylight hours. Furthermore, particular vigilance with bite precautions should be taken around dawn and dusk.
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Dr. Arvind Singh is M. Sc. and Ph. D. in Botany with an area of specialization in Ecology. He is a dedicated Researcher having more than four dozen published Research Papers in the Journals of National and International repute. His main area of Research is Restoration of Mined Lands. However, he has also conducted research on the Vascular Flora of Banaras Hindu University-Main Campus, India.
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