Characterization of the second wave of COVID-19 in India

The second wave of COVID-19, which began in India around 11 February 2021, has hit the country hard with daily cases reaching nearly triple the first peak value as on 19 April 2021. The epidemic evolution in India is complex due to regional inhomogeneities and the spread of several coronavirus mutants. In this study, we characterize the virus spread in the ongoing second wave in India and its states until 19 April 2021, and also examine the dynamic evolution of the epidemic from the beginning of the outbreak. Variations in the effective reproduction number (R-t) are taken as quantifiable measures of virus transmissibility. R-t value for every state, including those with large rural populations, is greater than the self-sustaining threshold of 1. An exponential fit on recent data also shows that the infection rate is much higher than in the first wave. Subsequently, characteristics of COVID-19 spread are analysed region-wise, by estimating test positivity rates ( TPRs) and case fatality rates (CFRs). Very high TPR values for several states present an alarming situation. CFR values are lower than those in the first wave, but are recently showing signs of increase as the healthcare system is being over-stretched with the surge in infections. Preliminary estimates with a classical epidemiological model suggest that the peak for the second wave could occur around mid-May 2021, with daily count exceeding 0.4 million. The study strongly suggests that an effective administrative intervention is needed to arrest the rapid growth of the epidemic.