Dengue is an important arthropod-borne viral disease that affects tropical and subtropical regions. It is caused by the dengue virus, which has four distinct serotypes, and is transmitted by Aedes mosquitoes. Secondary infection with a different serotype is a major risk factor for the more severe form of the disease, dengue hemorrhagic fever, due to antibody-dependent enhancement. Each year, around 100 million cases of dengue fever occur worldwide, mostly in tropical areas such as Southeast Asia, South Asia, and Central and South America.

1. DENGUEDENGUE

2. 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.

3. Causes of dengue

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VIRUS VIRIONS (THEVIRUS VIRIONS (THE
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DOTS NEAR THEDOTS NEAR THE
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7.  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

8. 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)