Dengue is a flavivirus, transmitted by the mosquito Aedes aegypti. WHO had identified it as one of the neglected tropical diseases in 2010. The maximum disease burden due to dengue is in south east Asian and western pacific countries. India is an endemic country for dengue. Every year during and after monsoon, the number of dengue cases peak. The small and transient water collections along with appropriate temperature range and relative humidity leads to higher vector density. There are four dengue virus serotypes – DENV 1 – 4. The infection with any one serotype provides lifelong immunity to that particular serotype only. The vector breeds mostly in domestic man made water storage objects. The female Ae. aegypti becomes infected with dengue virus after consumption of blood meal from a person suffering from the disease. The virus is transmitted by introduction of saliva into the wound of the person bitten. The secondary infections are generally seem to be the worse. The different pathological mechanisms involve T cell mediated antibody response cross reacting with vascular endothelium along with release different cytokines and mediators. There is an increase in capillary permeability which leads plasma leakage and shock.