INTRODUCTION Dengue is an acuteviral infection with potential fatal complications transmitted by the infectivebite of a particular female mosquito known as Aedes Aegypti and also by Ae.albopictus.
The dengue viruses consists of an antigenic sub- group ofvirus, serotype DENV1-4, within the genus Flavivirus, Family Flaviviridae. Dengue virus infection is a major, growing public healthproblem with an estimated 2.5 billion people at risk of infection. Dengueviruses can cause a wide variety of clinical illnesses ranging from mildlysymptomatic dengue fever (DF) to more dangerous clinical conditions withcapillary leakage syndrome such as dengue shock syndrome (DSS) and denguehemorrhagic fever (DHF).(1) It is a self limiting diseasefound in tropical and sub tropical regions around the world, predominantly inurban and semi-urban areas. Dengue Haemorrhagic Fever (DHF) which is a lethalcomplication was first recognized in 1950s during the dengue epidemic inPhilippines and Thailand.
The global prevalence of dengue has grownsignificantly in recent decades. The disease is now endemic in more than 100countries in South –East Asia, Western Pacific, Eastern Mediterranean, Africa,the America in which South –East Asia and Western Pacific are seriouslyaffected. Before 1970, only nine countries had experienced DHF epidemic, anumber that had increased more than fourfold by 1995.
WHO currently estimatesthat there may be 50 million cases of dengue infection worldwide every yearwith around 24,000 deaths. Transmission: Though vertical transmission ofthe virus has been reported , mosquitoes mainly acquire DENV by feeding on theblood of an infected human. DENV first infects and replicates in the mosquitomidgut epithelium. It subsequently spreads through the hemolymph to replicatein other organs such as the fat body and trachea, finally infecting thesalivary 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 bloodmeal, thus spreading the disease. The mosquito vectors, principallyAedesaegypti, become infected when they feed on humans during the usualfive-day period of viraemia.
The virus passes from the mosquito intestinaltract to the salivary glands after an extrinsic incubation period, a processthat takes approximately 10 days and is most rapid at high ambienttemperatures. Mosquito bites after the extrinsic incubation period result ininfection, which might be promoted by mosquito salivary proteins. Thetransmission area of this disease continues to expand due to many direct andindirect factors linked to urban sprawl, increased travel and global warming.(2)