Ans. b. Increased chances of DHFPATHOGENESIS OF DENGUE VIRUSPrimarily dengue infection occurs when a person is infected with dengue virus for the first time with any one serotype.Months to years later, a more severe form of dengue illness may appear (Called secondary dengue infection) due to infection with another second serotype which is different from the first serotype causing primary infection.The severity of secondary dengue infection occurs due to a unique immunological phenomenon called antibody dependent enhancement (ADE), i.e. non-neutralizing antibody produced against the first serotype will combine, cover and protect the second serotype from host immune response.ADE is remarkably observed when serotype 1 infection followed by serotype 2, which also claims to be the most severe form and prone to develop into Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS).Serotype 2 is more apparently more dangerous than other serotype.