DENGUEDENGUE

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.

Causes of dengue

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)