Wenesday Post

India failed to adequately prepare for the second wave of Covid 19 infections. Govt officials and health authorities are now routinely warning people of the possibility of a third wave. Principal Scientific Advisor to govt of India is calling the third wave inevitable even though its timing could not be predicted. But he also added that the third wave could be avoided through strong measures. Local administrations and hospitals have already begun ramping up their infrastructure in anticipation of the third wave.

Now what is a wave in an epidemic:

There is no textbook definition of what constitutes a wave in an epidemic. The term is used generically to describe the rising and declining trends of infections over a prolonged period of time. The growth curve resembles the shape of a wave. Historically, the term wave is used to refer to the seasonality of the disease. Several viral infections are seasonal in nature, and they recur after fixed time intervals. Infections rise and then come down, only to rise again after some time.

Covid-19 has continued relentlessly for the last one-and-a-half years, but in every geography, there have been periods of surge that have been followed by a relative lull. In India so far, there have been two very distinct periods of surge, separated by a prolonged lull.

Smaller regions within a country, a state, or a city, for example, would have their own waves. Delhi, for example, has so far experienced four waves. There are three very distinct peaks in its growth curve even before the current wave, while in states like Rajasthan or Madhya Pradesh, the growth curves had a much more diffused look until February, lacking a sharp peak. It would be difficult to identify distinct waves in such a situation.

Will the third wave be stronger?

There has been some speculation about the third wave being even stronger than the second. However, this is not something that can be predicted. Usually, it is expected that every fresh wave would be weaker than the previous one. That is because the virus, when it emerges, has a relatively free run, considering that the entire population is susceptible. During its subsequent runs, there would be a far lower number of susceptible people because some of them would have gained immunity.

This logic, however, has been turned on its head in India’s case. When the number of cases began declining in India after mid-September last year, only a very small fraction of the population had got infected. There was no reason for the disease spread to have slowed down, considering that such a large proportion of the population was still susceptible. The reasons for the five-month continuous decline in cases in India is still not very well understood.

And since the second wave was expected to be weaker than the first, many were fooled into believing that the pandemic was nearing its end. With the lessons learned in a very painful manner, there are now suggestions that the third wave might be even stronger.

But that might not be the case. A far greater number of people have been infected during the second wave than the first. With the positivity rate almost four times that of the first wave, the unconfirmed infections — those who were never tested — are also expected to be large. In addition, vaccination would also induce immunity in a large proportion of the population. So, there would be a significantly lower number of susceptible people in the population after the second wave.

However, gene mutations in the virus can alter these calculations. The virus can mutate in ways that make it escape the immune responses developed in the already infected people, or those vaccinated.

But there are many experts who feel that unless hit hard by the new Covid variant, chances of third-wave battering India are slim. The country has encountered no new lineage of the new Coronavirus so far after Delta variant was noticed a few months back. A wave occurs when there is a huge surge of an infectious disease. India has faced two-wave so far-the first in August-September of 2020 and the second starting March 2021. If there is no significantly faster spreading mutant, the third wave will be not very strong.

That the test positrivity rate (TPR), a key indicator of how widespread the transmission is, tose beyond 20% during April May 2021, but now it is settled around 2.5%. As per WHO guidelines, a TPR below 5 for a sustainable period means the transmission is much slower.The case fatality rate has also cone down to the pre- second wave levels of below 1%. The calculations of case fatality rate and TPR are based on seven day moving averages of daily cases, daily deaths and daily testing.

Besides, India’s rapid pace of vaccination is expected to come to rescue even if new mutation arrives. India has administrated 70 Cr+ doses so far amd more than 56% of the eligible population has been administrated by at least one dose.

So let us wait and watch, and in the mean time keep our fingers crossed.

Waiting for your views/comments.

Anil Malik

Mumbai, India

8^th September 2021.v