Evaluation of Platelet Count in Dengue Fever Along with Seasonal Variation of Dengue Infection

Introduction: Indian Subcontinent has emerged as a scene for mosquito-borne infectious diseases, like Malaria and Dengue fever. After the 1990s, the rate of Malaria has declined owing largely to preventive measures, but at the same time the rate of Dengue Fever (DF) and dengue hemorrhagic fever has increased to a larger extent. Objectives: 1) Evaluation of platelet count and the prevalence of Dengue Fever. 2) Seasonal variation of Dengue infection Materials and methods: The present study was conducted retrospectively for a period of 1 year during the recent outbreak of dengue fever in Davangere in the year 2009. Blood samples were collected from 1549 patients experiencing a febrile illness, clinically consistent with Dengue infection. Serological confirmation of Dengue Infection was done and platelet count was done in all the serologically positive cases. Case-inclusion criteria: All patients with clinical features and serologically positive dengue infections were included. Exclusion criteria: 1) Patients with thrombocytopenia but serologically negative were not included. 2) Patients with thrombocytopenia and no fever were not included. 3) A case was excluded, if routine laboratory testing suggested bacterial or any viral infection other than dengue infection or any other disease. Results: Out of 1549 suspected cases, 294 cases (18.97%) were confirmed as serologically positive. The difference between numbers of serologically positive cases during different months was significant. Larger proportions of serologically positive cases were observed among adults. Outbreak coincided mainly with the post monsoon period of subnormal rainfall. The difference between serologically positive cases as compared to serologically negative ones in post monsoon period was significantly higher. The difference in the rainfall and temperature between three seasonal periods was significant. Conclusion: This retrospective study highlighted rain, temperature and relative humidity as the major and important climatic factors, which could alone or collectively be responsible for an outbreak and also the drastic fall in the platelet count which is life threatening is highlighted. More studies in this regard could further reveal the correlation between the climatic changes, platelet count and dengue outbreaks, which would help in making the strategies and plans to forecast any outbreak in future well in advance.