Dengue in India.

Dengue virus belongs to family Flaviviridae, having four serotypes that spread by the bite of infected Aedes mosquitoes. It causes a wide spectrum of illness from mild asymptomatic illness to severe fatal dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS). Approximately 2.5 billion people live in dengue-risk regions with about 100 million new cases each year worldwide. The cumulative dengue diseases burden has attained an unprecedented proportion in recent times with sharp increase in the size of human population at risk. Dengue disease presents highly complex pathophysiological, economic and ecologic problems. In India, the first epidemic of clinical dengue-like illness was recorded in Madras (now Chennai) in 1780 and the first virologically proved epidemic of dengue fever (DF) occurred in Calcutta (now Kolkata) and Eastern Coast of India in 1963-1964. During the last 50 years a large number of physicians have treated and described dengue disease in India, but the scientific studies addressing various problems of dengue disease have been carried out at limited number of centres. Achievements of Indian scientists are considerable; however, a lot remain to be achieved for creating an impact. This paper briefly reviews the extent of work done by various groups of scientists in this country.

Molecular approach to the development of flavivirus vaccines

The Flaviviridae is a family of about 70 mostly arthropod-borne viruses many of which are major public health problems with members present in most continents. Among the most important are yellow fever (YF), dengue (DEN) with its 4 serotypes and Japanese escephalitis (JE) virus. A live attenuated virus is used as a cost-effective, safe and efficacious vaccine against YF but no other live flavivirus vaccines have been licensed. The development of recombinant DNA technology and its application to study flavivirus genome structure and expression has opened new possibilities for flavivirus vaccine development. The new approaches include the use of cDNAs encompassing the whole viral genome to generate infectious RNA after in vitro transcription. This methodology allows the genetic mapping of specific viral functions and the design of viral mutants with considerable potential as new live attenuated virues. The use of infectious cDNA as a carrier for heterologous antigens is a gaining importance since chimeric viruses are shown to be viable, immunogenic and less virulent in some cases as compared to the parental viruses. The use of DNA to overcome intrinsic mutation rates of RNA virus populations in conjunction with vaccine production in cell culture should improve the reliability and lower the cost of live attenuated vaccines.