How to quantify the extent of and response to COVID-19 (or other pandemics)

The COVID-19 pandemic started spreading across India in March, and till today, opinions vary widely on how the spread of the disease has affected different administrative regions, and how well they have mitigated the circumstances. Various numbers are quoted and there is no consensus, primarily because the situation is dynamic and India is a large and heterogeneous country. I bind all these effects in one simple quantitative measure, and demonstrate its robustness.