ABSTRACT
ackground: Dengue fever is caused by mosquito borne arbovirus of family Flaviviridae, Aedes agypti as the principle vector. In the recent past Delhi has witnessed several outbreaks affecting thousands of individuals and many of them get re-infected during subsequent years forming a bulk of secondary dengue cases putting them at risk of developing severe dengue.Methods: A total of 150 serum samples from suspected dengue cases were tested for dengue fever by NS-1 antigen and IgM antibody enzyme-linked immunosorbent assay (ELISA) followed by categorization into primary and secondary dengue using IgG avidity ELISA.Results: Out of total 150 clinically suspected dengue cases, 56 were positive either by Dengue NS-1 antigen or dengue IgM antibody or both. On the basis of dengue IgG avidity ELISA among 56 diagnosed dengue cases, 30 (53.57%) were found to be of secondary dengue.Conclusions: There is increasing trend of dengue cases in Delhi since past one decade. Being hyper-endemic area for dengue, more than 25% population have been reported to have past infection of dengue. Due to increased prevalence and simultaneous circulation of more than one serotypes, number of secondary dengue cases is also increasing. Since majority of severe dengue cases are associated with secondary dengue, early diagnosis and treatment can significantly reduce the fatal outcome. Thus, avidity testing for IgG antibody becomes an important tool.