The present specification discloses methods of determining risk of developing Dengue Hemorrhagic Fever/Dengue Shock Syndrome (DHF/DSS) in an individual infected with dengue virus (DV). The methods comprise determining, in a fluid or tissue sample of an individual, the presence, absence or quantity of dengue virus protein NS1, and determining, in a fluid or tissue sample of the individual, presence, absence or quantity of SC5b-9 complement complex. The methods can further comprise comparing the levels of NS1 protein and SC5b-9 complement complex with a database comprising epidemiological data correlating levels of NS1 protein and SC5b-9 complement complex with probability of developing DHF/DSS in a population.