Comparison of the epidemiological features of COVID-19 patients in the first and second waves: A study from South India.

Introduction: The coronavirus disease 2019 (COVID-19) pandemic has seen multiple surges globally since its emergence in 2019. The second wave of the pandemic was generally more aggressive than the first, with more cases and deaths. This study compares the epidemiological features of the first and second COVID-19 waves in Kozhikode district of Kerala and identifies the factors associated with this change. Methods: A comparative cross-sectional study was conducted in Kozhikode district. A total of 132,089 cases from each wave were selected for the study using a consecutive sampling method. Data were collected from the District COVID-19 line list using a semistructured proforma and analyzed using Statistical Package for Social Sciences (SPSS) ver. 18. Results: The second wave had a higher proportion of symptomatic cases (17.3%; 20.1%), cases with severe symptoms (0.3%; 0.6%), intensive care unit (ICU) admissions (11.2%; 17.9%), and case fatality rate (0.69%; 0.72%). Significant difference was noted in the age, gender, locality, source of infection, comorbidity profile, symptom, and the pattern of admission in various healthcare settings between the first and second wave. Among the deceased, gender, duration between onset of symptoms and death, comorbidity status, and cause of death were significantly different in both waves. Conclusion: The presence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant, as well as changes in human behavior and threat perception as the pandemic progressed, resulted in significant differences in various epidemiological features of the pandemic in both waves, indicating the need for continued vigilance during each COVID-19 wave.