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WHAT IS DENGUE ?
Dengue is one of the most important arthropod-borne
viral diseases in terms of human morbidity and
mortality. Dengue has become an important public
health problem. It affects tropical and subtropical
regions around the world, predominantly in urban and
semi urban areas.
Dengue fever and Dengue Heomorrhagic (severe
dengue) are caused by DENGUE FEVER VIRUS (DENV)
which is an RNA virus of the family Flaviviridae.
It is transmitted by Aedes aegypti and Aedes albopictus.
A TEM A TEM MICROGRAPH MICROGRAPH
SHOWING DENGUE SHOWING DENGUE VIRUS VIRIONS VIRUS VIRIONS
(THE CLUSTER OF (THE CLUSTER OF DARK DOTS NEAR DARK DOTS NEAR
THE CENTRE)THE CENTRE)
There are four distinct serotypes, DEN-1, 2, 3 and 4. Each episode of
infection induces a life-long protective immunity to the homologous
serotype but confers only partial and transient protection against
subsequent infection by the other three serotypes.
Secondary infection is a major risk factor for DHF due to antibody-
dependent enhancement.
Other important contributing factors for DHF are viral virulence, host
genetic background, T-cell activation, viral load and auto-antibodies.
All four serotypes can be isolated at any one time but the predominant
circulating dengue virus will show a sinusoidal pattern (Figure 5).
For example, DEN-3 was the predominant serotype in the early 90s with a
peak in 1993, and then subsequently declined. It then re-emerged,
reaching the peak in 2001. Other serotypes had been observed to be co-
circulating at the same time
Each year, an estimated 100 million cases of dengue fever occur worldwide.
Most of these are in tropical areas of the world with the greatest risk
occurring in:
•The Indian subcontinent
•South-east Asia
•Southern China
•Taiwan
•The Pacific Islands
•The Caribbean (except Cuba and the Cayman Islands)
•Mexico
•Africa
•Central and South America (except Chile, Paraguay and Argentina)