Dengue virus is widely distributed throughout the tropics and subtropics. The name ‘dengue’ has been derived from Swahili, meaning a sudden seizure by a demon. In 1780, an epidemic was reported in Philadelphia, where the name ‘break-bone fever’ was coined.
Dengue fever shows similarity in symptoms of Chikungunya and O’nyong-nyong viruses. Four types of dengue viruses exist: DEN 1, DEN 2, DEN 3 and DEN 4. Dengue stands in the first place among the diseases that are caused by vectors. It has been affecting about 2.5million people in 200 countries all over the world.
The virus enters the human through the saliva of the mosquito during the bite. It attaches to the WBC’s and multiplies inside them. The number of platelets decreases, thereby interfering with the clotting process. This is the cause of one of the most important problems of dengue, which is the risk of bleeding.
Dengue is presented clinically after an incubation period of 2-8days. It starts off with sudden fever accompanied by headache, redness in the eye as the superficial blood vessels of the conjunctiva become prominent, pain in the back and limbs, lymphadenopathy (swollen or enlarged lymph), retrobulbar pain (behind the eyeball) and maculopapular rash (flat red area on the skin).
The recovery phase is followed after infection. It mainly involves the restoring of fluids in the blood. This period is often associated with harsh itching and reduced heart beating rate.
The regions where rashes appeared, starts to peel off. This period is a time where the fluid in the body increases enormously, leading to loss of consciousness and constant tiredness.
In rare cases, neurological disorders along with impairment of internal organs like liver and heart results.
The fever is typically a bi - phase and lasts for 5-7 days. It may also occur in more serious forms such as hemorrhagic manifestations (dengue Hemorrhagic fever) or shock (dengue shock syndrome). They are more common in previously healthy children in the native populations of prevalent areas.
There may also be a hypersensitive response to sequential dengue virus infection in persons, previously sensitized by exposure to other serotypes of the virus.
Dengue virus is transmitted from one person to another by Aedes aegypti mosquitoes. The external incubation period is 8-10 days. Humans are the only identified vertebrate host. Sometimes the life cycle of the mosquito may also involve monkeys, squirrels and other forest animals. Blood transfusion without proper checking can also cause the spread of the disease.
Dengue was initially confined only to the east coast of India and has caused epidemics, along with the Chikungunya infections. In certain cases, both the virus had been isolated from the same patient.
Demonstrating the presence of circulating IgM antibody provides an early diagnosis of dengue. These antibodies usually start to appear within two to five days of the onset of illness and remains in the blood for one to three months.
Control of dengue is only through controlling vectors. No vaccines had been identified for the effective prevention. Oral rehydration or providing fluids intravenously are effective to maintain fluids in the body.