Numbers Matter | Covid-19: Three waves, three paces

India’s third wave has truly peaked and is now receding fast — giving us the unique chance to compare it to the two previous waves.

With 85,045 new Covid-19 infections detected across India on Sunday, the national daily tally fell below the 100,000-mark for the first time in more than a month — a clear indication that India’s third Covid-19 wave is contracting nearly as fast as it soared.

If we look at the case curve in these three waves purely in terms of when they started, there is a stark difference in terms of how prolonged each of the waves was. (iStock)

This was the first time since January 5, or 32 days ago, that there were fewer than 100,000 cases in a single day. On Monday, the daily case tally was 66,156 — dropping further. For context as to how much this number has dropped in recent days, just 19 days ago there were more than five times as many cases — on January 20, there were 347,487 new infections of Covid-19 detected across India.

With this, the seven-day average of daily cases has now dropped to 124,368 for the week ended Sunday. This number, which is used to denote a region’s case curve, has now dropped 60% from the peak level of 312,180 cases a day (on average) seen for the week ended January 25. In simpler terms, in less than two weeks since it touched a peak, the Indian case curve has already shrunk to more than half its volume.

This trend clearly shows that India’s third wave has well and truly peaked and is now receding fast — giving us the unique chance to compare it to the two previous waves.

If we look at the case curve in these three waves purely in terms of when they started (from the point a previous wave bottomed out), there is a stark difference in terms of how prolonged each of the waves was. The first wave, which technically started March 3, 2020 (the day the first outbreak case was reported in the country), peaked on September 16, 2020 — taking exactly 196 days from start to peak. At its highest point, the seven-day average of daily cases in this wave touched 93,617. From thereon, it eventually then continued a long and slow drop till early February 2021.

The slowest of the three, the slow and long nature of the first wave is easily explained by the hard lockdown imposed in the country starting March 24, 2020. Curbs to varying degrees remained in place in the country through much of 2020, lasting till June — from where a slow and gradual unlocking started (which lasted several months). These curbs ended up buying plenty of time for the government to enhance resources like hospitals and testing facilities to suit the Covid-19 pandemic.

In contrast, the second wave (caused by the Delta variant) started on February 12, 2021, when the case curve bottomed out at 11,053. The second wave saw a much more abrupt rise in cases as there were next very few (if at all) curbs on social gatherings in place by the start of 2021. By May 9 that year, the case curve had soared to a whopping 391,819 (the highest it has ever soared, at least in recorded terms) — this means that the second wave went from start to peak around three months (87 days).

Cases then proceeded to see a similarly quick drop across the country, after which it settled into a long and slow decline. This decline, in fact, ended up lasting much longer and continued till the end of 2021. Experts have said this was because recorded seropositivity in the country soared to as much as 97% in some urban centres like Delhi, which meant that almost everyone in these regions was exposed to the virus at some point. This ended up buying a lot of time before the onset of the third wave.

The third wave officially kicked off in the country on December 26, 2021, when the seven-day average of daily cases in the country bottomed out at 6,641 — a paltry figure for a nation the size of India. From there on, however, cases grew at a rate never seen before due to the highly transmissible nature of the Omicron variant that was causing this spurt in infections. By January 25, the case curve had peaked at 312,180 infections a day — placing its start-to-peak time of exactly a month (31 days).

While many health experts have repeatedly stressed that the real peak of the Omicron surge was far higher in the country, a lot of people resorted to using home test kits due to milder symptoms (or none at all) occurring with the Omicron variant. These were not necessarily be followed up with an RT-PCR test if they were positive, thereby keeping them off the radar. There is no way to map these cases since most mild patients are recovering in home isolation. But while the intensity of the third wave remains a topic of debate and analysis, it is not true for the timing. The short nature of the third wave is a phenomenon reported in all regions across the world that have seen Omicron surges.

So, what effect did it have on deaths?

This gives us a good base point from which to look at the level of deaths in each of these waves. When similar cut-off dates are used to organise the death curves (seven-day average of daily deaths) in the three waves, two key takeaways can be observed.

The first is the time taken for each of these peaks. In the first wave, cases peaked almost exactly in sync with the cases — the peak in deaths came on September 17, 2020 (197 days since the start of the wave), just one day after cases peaked in that wave. In the second wave, the peak in deaths came on May 23, 2021 — 101 days since the start of the wave, or exactly two weeks after cases peaked in that wave. In the third wave, the peak in deaths was witnessed on February 4, 2022 — 44 days since its start, and 13 days after the peak of cases.

If we look at the case fatality rate (CFR) at the peak of each wave, we see that with each progressive wave, the country is getting better at saving lives. Comparing the deaths and cases at their peaks, the CFR at the peak of the first wave was 1.25%, while it was 1.07% at the peak of the second wave, and only 0.36% at the peak of the third.

But there are some caveats that must be mentioned here.

First, as time has progressed, it is not surprising that the world is getting better at saving lives from Covid-19. Over the course of the two years of the pandemic, doctors across the world have honed the treatment, medicines, and resources (such as Oxygen) needed for the treatment of the disease, and as such have been devising better ways for treatment.

Second, is the impact of vaccination. In each subsequent wave, the proportion of people vaccinated in the country has been increasing. At the peak of the first wave, no vaccine had been developed for the disease, so not a single person in the country (or the world) had been vaccinated. At the peak of the second wave, only 12% of the country’s adults had received a shot of the vaccine. This proportion had soared to 95% at the peak of the third wave.

Finally, is the consistency in reporting of deaths. The biggest inconsistency in reporting (what some experts say was missing the reporting of) deaths was during the brutal second wave in the country. This is evident from the fact that several states across the country continued to reconcile their death figures weeks and months after the second wave — a fact visible in the repeated spike in the death curve seen in Chart 2. This was because, at its peak, the country’s health infrastructure was so heavily burdened, that several thousand deaths ended up getting misreported. In fact, independent analyses done by several experts in the field have repeatedly shown that several states appear to have undercounted deaths by several-fold in the second wave. This implies that the CFR during the second wave may have in fact been much higher, either the same or even higher than the first wave.

In addition, it also highlights how well the country appears to have performed in the third wave, in terms of deaths — where the death curve never even went above the first wave, which saw fewer than a third of the cases seen during the Omicron surge.

If the pandemic has taught us anything, it is the value of data. To help understand the battle against the pandemic, Jamie Mullick, HT’s Covid data whiz, writes Numbers Matter

The views expressed are personal