Area under curve vs height of curve

Second wave's certainly more intense, but is it worse (Mumbai case study)

(If viewing grim deaths through a statistical lens makes you queasy, don’t read ahead.

If you have lost a loved one or are struggling with Covid now, I’m truly sorry . )

How does 2nd wave compare to first? Worse, say most.

But how can it be so with all those antibodies & vaccinations? Puzzling.

I use Mumbai data and basic analysis to see if there’s a different perspective on above questions. While I avoid making or using predictions, I do have implicit expectations of the future. Compared to these, intensity of second wave in Mumbai surprised me. I never thought we’d get to 7-day average of 70 deaths/day (vs peak of 120 in first wave) after nearly two-thirds of Mumbai’s vulnerable had either antibodies or vaccinations.

However, from a different perspective, picture looks different. Look at cumulative numbers rather than peak intensity. In first wave (till end-March), Mumbai lost 11,500 lives. Deaths/day peaked after 6,000 lives had been lost and cases/day peaked after 9,000 lives had been lost. In second wave, cases/day have already peaked and have been declining for two weeks (no guarantee trend won’t reverse, though all of us fervently hope trend holds). More reliably, test positive rate has also declined to sub-10%. In second wave, Mumbai has lost 1,500 lives till date with deaths yet to start declining.

Statutory warning that we’re entering unreliable forecasting domain that I’m terrible at. If deaths decline with a lag to cases, May could still be as bad as April but June could see a return to March sanity. If decline follows spike, Mumbai’s second wave could witness 3000+ cumulative deaths. Fewer if decline is sharper as panic subsides and healthcare capacity responds better.

It’s clear that Mumbai’s second wave was far more intense than first. Peak cases/day and base of active cases were over 3x that of first wave. Peak deaths/day less so, but still uncomfortably high at 60% of first wave. However, when the wave passes, cumulative lives lost may be 25-30% of first wave, a number more consistent with prior immunity and decent vaccination coverage of most vulnerable. More intense, but less bad overall.

My aim is primarily to offer a different, evidence-based perspective on the world around me, and see how it fits with our qualitative understanding of how the world works. It is not to make a prediction or change professions into sham epidemiology (already overcrowded). Please read this in that spirit. In theory, this analysis could be repeated for other parts of India. However, second wave is yet to start receding in other parts and it’s probably more robust to wait before attempting something similar.

[PS. I usually get questions about data reliability. All covid data around the world has ‘natural’ under-counting, partly due to nature of disease (vast majority don’t notice it) and partly due to systemic incentives/distortions. Broader debate is above my pay-grade and conspiracy theories are outside my interest. However, Mumbai’s test positive rate was ~11% in first wave and ~13% in second wave, indicating that making above comparison isn’t unreasonable. ]