Proportion of Dengue Cases Before and During the COVID-19 Pandemic: A Retrospective Study

Introduction: Dengue is a viral haemorrhagic fever that has become endemic in most tropical and subtropical countries, including India. There is a well-established surveillance system in India, where cases are notified in real time. The Coronavirus Disease 2019 (COVID-19) pandemic came as a learning tool, as the entire world concentrated on control and preventive measures, while relatively little attention was given to endemic diseases. Aim: The present study aimed to determine the proportion of dengue cases before and during the pandemic, along with seasonality and seroprevalence. Materials and Methods: This retrospective study was conducted from January 2018 to December 2024 at Rajarajeswari Medical College and Hospital, Bengaluru, Karnataka, India. The study population included all patients referred to the Microbiology department with suspected dengue. All samples were processed by immunochromatographic assays detecting IgM, IgG, and NS1 antigen according to standard protocols. The study included patients of both genders aged 5 to 60 years. Results were entered into log registers and maintained. The data were collected, compiled, and analysed to understand the prevalence of dengue in the area. Data were collected retrospectively from January 2018 to December 2024. Descriptive statistics were employed, and results were summarised in tables and figures; p-values were determined. Results: In the present study, the total number of dengue-positive tests was 3173 from January 2018 to December 2024. The highest number of cases was reported in 2019 (1,108), followed by 327 cases during the during pandemic (2020-2022). There was a 73% reduction in the number of cases. The highest number of cases was reported from June to September, followed by a gradual decline. In our study, the most common immunological marker was NS1, indicating acute infection, followed by IgM. Conclusion: Before and after the pandemic, the number of dengue cases reportedly increased fourfold. There was an unforeseen reduction in the number of cases during the pandemic; surveillance systems, as well as control and preventive measures for endemic diseases, were at a halt. There is a need for a parallel healthcare system that can function as two sides of a coin, managing both pandemics and endemic diseases.