Dengue Research in India

Dengue fever is currently a serious public health problem in India. Several outbreaks of dengue (>50) have been reported in different parts of the country in the past few decades. Due to the enormity of the problem, several studies are being conducted in India and other parts of the world to comprehend the extent of problem of dengue fever, analyse the situation with respect to occurrence and distribution vector, study of the virus, and vaccine development.

The Aedes Aegypti Mosquito

Studies on occurrence and vector distribution have noted that the breeding of Aedes aegypti begins in June itself (that is onset of monsoon). In some regions, the urban house index of Aedes aegypti was observed higher in pre-rain periods than in post-rain periods. This is probably due to water shortage in the pre-rain period which leads to the storage of more and more water which in turn promotes vector prominence in human habitations. The fact that Aedes aegypti index increases from June (and in some areas before the rainy season), advance planning for dengue prevention and control can start in this period with vector surveillance and control measures throughout the rainy season.

Dengue Vaccine

Currently there is no vaccine for dengue fever even though vaccine research for dengue was started in the 1940s. Several studies are being done to make a successful vaccine but this objective has not been realised. There are several problems in making a successful dengue vaccine such as:

• Dengue is caused by four types of dengue virus (DEN-1, DEN-2, DEN-3 and DEN-4) and an effective vaccine should induce immunity against all four viruses concurrently.
• Infection with any type of dengue virus leads to dengue fever and thereafter lifelong protective immunity against that particular type of infecting virus (homotypic immunity). However, a second infection with any type of dengue virus (e.g. DEN-1 followed by DEN-4) can cause severe and even fatal dengue infection (dengue hemorrhagic fever, dengue shock syndrome). Hence a major concern is with the vaccine is that if it does not lead to the development of immunity against all the four related virus vaccination, then it can lead to potentially severe dengue infection. Besides being safe and effective the dengue vaccine should also be inexpensive.

Several vaccines are undergoing clinical trial but still a safe and effective vaccine has not been developed. Further studies and research on dengue vaccine are needed.