PROPORTION OF PRIMARY AND SECONDARY DENGUE INFECTION AMONG SEROLOGICALLY POSITIVE DENGUE FEVER CASES ADMITTED IN A TERTIARY CARE CENTRE IN KERALA

ABSTRACT Introduction: Dengue fever is the most rapidly spreading mosquito borne viral disease in the world. In the recent decades global incidence of dengue has significantly increased. India is endemic for dengue so is Kerala state. Increased population growth, urbanisation, lack of efficient mosquito control programme contribute to its spread. Secondary dengue infection is more prone to develop complications such as DHF and DSS. Objectives: The present study was conducted to estimate the proportion of primary and secondary dengue infection among serologically positive dengue fever cases admitted in Government medical college Ernakulam. Methods: This descriptive cross-sectional study conducted at Government Medical College Ernakulam included 450 clinically suspected cases of dengue whose blood samples were received in Microbiology lab for testing. Clinical history of patients was taken from case records. NS1, IgM, and IgG ELISA were performed with serum from each sample according to manufacturer’s instructions. To detect the proportion of primary and secondary dengue cases, IgM to IgG optical density ratio was calculated in those samples positive for NS1/IgM/IgG. IgM/IgG optical density ratio more than 1.2 indicated primary dengue infection and IgM/IgG optical density ratio less than 1.2 indicated secondary dengue infection. The data was entered in the excel spread sheet as per proforma and was analysed using SPSS software. Chi square test was used for analysis of study variables. The level of significance was taken as p value < 0.05. Results: Out of the 450 samples tested, 147(32.66%) were found to be positive for dengue. Secondary dengue infection was more (56.4%). Conclusion: The proportion of dengue positivity was comparable to many other studies done in India. Secondary dengue infection was more in our study which can be attributed to hyperendemicity of dengue in Kerala. Keywords: Primary dengue, Secondary dengue, Dengue hemorrhagic fever, Dengue shock syndrom