INTRODUCTION epidemic, a number that had increased more than

 

 

INTRODUCTION

 

 Dengue is an acute
viral infection with potential fatal complications transmitted by the infective
bite of a particular female mosquito known as Aedes Aegypti and also by Ae.
albopictus. The dengue viruses consists of an antigenic sub- group of
virus, serotype DENV1-4, within the genus Flavivirus, Family Flaviviridae.

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                Dengue virus infection is a major, growing public health
problem with an estimated 2.5 billion people at risk of infection. Dengue
viruses can cause a wide variety of clini­cal illnesses ranging from mildly
symptomatic dengue fever (DF) to more dangerous clinical conditions with
capillary leakage syndrome such as dengue shock syndrome (DSS) and dengue
hemorrhagic fever (DHF).(1) It is a self limiting disease
found in tropical and sub tropical regions around the world, predominantly in
urban and semi-urban areas. Dengue Haemorrhagic Fever (DHF) which is a lethal
complication was first recognized in 1950s during the dengue epidemic in
Philippines and Thailand. The global prevalence of dengue has grown
significantly in recent decades. The disease is now endemic in more than 100
countries in South –East Asia, Western Pacific, Eastern Mediterranean, Africa,
the America in which South –East Asia and Western Pacific are seriously
affected. Before 1970, only nine countries had experienced DHF epidemic, a
number that had increased more than fourfold by 1995. WHO currently estimates
that there may be 50 million cases of dengue infection worldwide every year
with around 24,000 deaths.

 

Transmission:

Though vertical transmission of
the virus has been reported , mosquitoes mainly acquire DENV by feeding on the
blood of an infected human. DENV first infects and replicates in the mosquito
midgut epithelium. It subsequently spreads through the hemolymph to replicate
in other organs such as the fat body and trachea, finally infecting the
salivary gland at approximately 10–14 days post-bloodmeal. Once in the saliva,
DENV can be inoculated into a human host when the mosquito acquires a blood
meal, thus spreading the disease. The mosquito vectors, principally
Aedesaegypti, become infected when they feed on humans during the usual
five-day period of viraemia. The virus passes from the mosquito intestinal
tract to the salivary glands after an extrinsic incubation period, a process
that takes approximately 10 days and is most rapid at high ambient
temperatures. Mosquito bites after the extrinsic incubation period result in
infection, which might be promoted by mosquito salivary proteins. The
transmission area of this disease continues to expand due to many direct and
indirect factors linked to urban sprawl, increased travel and global warming.(2)