Epidemiological Dynamics of the COVID-19 Pandemic in India: An Interim Assessment

We have analyzed the time-series for the number of active cases of COVID-19 pandemic in India, as well as, in other countries around the world using a variety of statistical fitting procedures. We obtain robust estimates of the exponential growth rate for the number of active cases, which is then used for calculating the reproduction number of the epidemic. We estimate the basic reproduction number of COVID-19 epidemic in India to be R-0 similar to 1.82 +/- 0.02, a value that lies at the lower end of the spectrum of values of different regions around the world where there have been major outbreaks of the disease. We have also investigated the change in the effective reproduction number over time, particularly following the introduction of unprecedented non-pharmaceutical interventions such as the stay-at-home order (lockdown) imposed over the entire country from 24 March 2020, and continued at varying levels of strictness, and with regional variations, up to the present (July). We observe that the reproduction number showed a large reduction within a couple of weeks of the imposition of lockdown, suggesting that this measure played a role (along with others such as compliance with physical distancing rules in public and use of masks) in reducing the rate of spreading of the contagion, although it was unable to break the chain of infection. We also note that there is considerable regional variation across India in the dynamics of the epidemic, with different regions registering rise and fall in the growth rate of the disease at different times.