Two years on: What we’ve learnt from the outbreak

March 2 marks the completion of the second year of India’s ongoing battle with the global Covid-19 pandemic. The country’s first case of domestic transmission of Covid-19 was detected on this date in 2020, when two foreign returnees (one in Delhi and the other in Telangana) tested positive. In these two years, the country has recorded nearly 43 million infections and at least 514,000 deaths, with the actual numbers likely to be higher.

The second anniversary comes with infections at a low, and 95% of the eligible population (around a billion people over the age of 15) having been partly vaccinated (78% is fully vaccinated). Monday saw 5,804 new cases of Covid-19, the lowest in 70 days, and the second-lowest in nearly 650 days. This indicates that the third wave is not only receding, but cases are also falling to levels that are among the lowest in these two years.

With India having gone through three distinct waves of infections, how the pandemic unfolded through the two years has left behind troves of data on the virus’ spread in both statistical and epidemiological terms, giving us the unique chance to look at how these surges have behaved.

Three waves, and three distinct paces

If we look at the case curve in these three waves in terms of duration, a stark difference is visible in their nature. The first wave, which started March 3, 2020, peaked on September 16, 2020, taking exactly 198 days from start to peak. It was the longest of the three waves. At its highest, the seven-day average of daily cases touched 93,617 – the lowest of the three. This long-and-flat nature of the first wave is easily explained by the hard lockdown imposed on March 24, 2020. Curbs to varying degrees remained in place through much of 2020.

In contrast, the second wave caused by the Delta variant started from February 12, 2021. It saw a much more abrupt rise in cases as there were few curbs by the start of 2021. By Day 87, the case curve soared to a whopping 391,819, the highest of the three waves. Cases then proceeded to see a similarly quick drop across the country, after which it settled into a long and slow decline.

The third wave kicked off on December 27, 2021. Cases then grew at a rate never seen before due to the highly transmissible Omicron variant. By Day 30, the case curve peaked at 312,180 infections a day. In just 64 days since its start, the Omicron wave has already dropped to a seven-day average of 11,538 daily cases, roughly the same level when the first wave ended.

Thus, the first wave peaked at around a quarter (24%) of the peak of the second wave, which was the highest. And the third wave saw a peak that was 80% of the highest point of the second wave.

Chart 1: Daily cases in three waves

Despite rapid increase, third wave saw fewest infections

Another way to look at these waves is the total number of infections caused in each of these surges. While the first wave dragged on for nearly a year (346 days from start to finish), it ended up causing 10.9 million infections.

In contrast, the brutal Delta-driven second wave resulted in nearly 24 million total infections of Covid-19 over 318 days. 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 almost everyone in these regions was exposed to the virus.

The third and shortest wave so far is currently in its 64th day and dropping fast. It has thus far resulted in 8.1 million cases. To be sure, health experts have repeatedly stressed that the real volume of infections in the Omicron surge may have been far higher, as a lot of people resorted to using home test kits due to milder symptoms (or none at all), thereby staying off the radar. There is no way to map these cases since most mild patients recovered in home isolation.

Chart 2: Total Covid-19 cases reported in three waves

What effect did it have on deaths?

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

The first is the time taken to peak. In the first wave, deaths 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, and 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 seen on February 4, 2022, 44 days since its start, and 13 days after the peak of cases.

The second wave, where the seven-day average of daily deaths peaked at 4,191, was the highest peak by a large margin. Despite this, it was also most likely to have been underreported (more on this later). The first wave saw a peak of 1,169 daily deaths – 28% of the second wave peak.

Interestingly, even at its worst, the third wave peaked at 1,133 – not only just 27% of the highest point of second wave, but the lowest of all three waves.

Chart 3: Daily deaths due to Covid-19 in three waves

Getting better at saving lives

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

Chart 4: CFR, peak of cases in each wave with respect to peaks deaths

But there are some caveats. First, as time progressed, it is not surprising that the world is getting better at saving lives. Over the course of the two years of the pandemic, doctors across the world have arrived at and have access to treatment, medicines and resources needed to battle the disease.

Second, the impact of vaccination. In each subsequent wave, the proportion of the 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 had been vaccinated. At the peak of the second wave, only 12% of the country’s adults had received a shot. This proportion soared to 95% of those eligible at the peak of the third wave.

The third, consistency in reporting of deaths. The biggest inconsistency in reporting 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 being misreported.

In fact, independent analyses done by several experts have repeatedly shown some states appear to have undercounted deaths by several multiples 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.

Lastly, and most importantly, how well the country appears to have performed in the third wave in terms of saving lives.