Characterization of the Second Wave of COVID-19 in India

Ranjan, R.; Sharma, A.; Verma, M. K.

Background: The second wave of COVID-19 is affecting most of the world. The scenario is very grim in India where the daily count on April 15, 2021 itself is double of the first peak. The epidemic evolution there is quite complex due to regional inhomogeneities. In this paper, we characterize the virus spread in the ongoing second wave in India, as well as study the dynamical evolution of epidemic from the beginning of the pandemic. Methods: Variations in the effective reproduction number (Rt) in India are taken as a quantifiable measure of the virus transmissibility and are compared with those of other countries where the second wave is already over. Further, characteristics of COVID-19 spread are analyzed for Indian states by estimating test positivity and case fatality rates. Finally, forecasts and actionable inputs are provided based on mathematical and epidemiological models. Results: Effective reproduction number for almost every state in India has value greater than 1 indicating the presence of the second wave. An exponential fit on recent data indicates that the infection rate is much higher than the first wave however the case fatality rate is lower. Preliminary estimates with the SIR model suggest the peak for the second wave to occur in mid-May 2021 with daily count exceeding 0.35 million. Conclusions: The spread of the second wave is much faster than the first wave. Hence, quick and effective administrative intervention is needed to arrest the rapid growth of the epidemic.