The virus

00000000Dengue virus belongs to the family Flaviviridae. The four serotypes of dengue virus (designated DEN-1, DEN-2, etc.) can be distinguished by serological methods. Infection in humans by one serotype produces life-long immunity against reinfection by that same serotype, but only temporary and partial protection against the other serotypes. Dengue viruses share many characteristics with other flaviviruses, having a single-stranded RNA genome surrounded by an icosahedral nucleocapsid and covered by a lipid envelope. The virion is approximately 50 nm in diameter. The flavivirus genome is approximately 11 kb (kilobases) in length, and the complete genome sequence is known for isolates of all four serotypes of dengue virus. The gonome is composed of three structural protein genes, encoding the nucleocapsid or core pretein (C), a structural (NS) protein genes. The domains responsible for neutralization, fusion and interactions with virus receptors are associated with the envelope protein. The order of proteins encoded is 5'-C-prM-M-E-NS1-NS2A-NS2B-NS3-NS4A-NS4B-NS5-3'.

The vectors

00000000 Ae. Aegypti is a tropical and subtropical species of mosquito found around the globe, usually between latitudes 35^oN and 35^oS, approximately corresponding to a winter isotherm of 10^oC as shown in Figure 1.2. Although Ae. Aegypti has been found as far north as 45^oN, such invasions have occurred during the warm season, and the mosquitos have not survived the winters. Distribution of Ae. Aegypti is also limited by altitude. It is usually not found above 1 000 m but has been reported at 2121 m in India, at 2200 m in Colombia, where the mean annual temperature is 17^oC, and at 2400 m in Eritrea. Ae. Aegypti is one of the most efficient mosquito vectors for arboviruses, because it is highly anthropophilic and thrives in close proximity to humans and often lives indoors. Dengue outbreaks have also been attributed to Ad. Albopictus, Ae. Polynesiensis, and several species of the Ae. Scutellaris complex. Each of these species has its own particular geographical distribution; however, they are less efficient epidemic vectors than Ae. Aegypti. While vertical (possibly transovarian) transmission of dengue viruses has been demonstrated in both the laboratory and the field, the significance of this to maintenance of the virus has not been established. A factor complicating eradication of the vector is that Ae. Asgypti eggs can withstand long periods of desiccation, sometimes for more than a year.
The host