R Sukumar
Hindustan Times, New Delhi

With India escaping the post-Diwali surge, if its current Covid disease trajectory stays in the plateau in which it finds itself till the end of the month, it is likely (a low but significant probability) that the second wave in India will be less intense. (AP Photo)



Last week, as several instalments of this column had pointed out, was going to be crucial for India in terms of how the trajectory of the coronavirus disease would play out in the country. It was to show whether India too would see the holiday effect seen in almost every other country where mass festivities and celebrations resulted in a spike in cases weeks later. Diwali, perhaps the biggest festival in India, was in mid-November, and if daily case numbers were going to rise on account of the parties, family gatherings and travel associated with the celebrations, last week is when this would have shown up. The week has come and gone. We are now on December 7, and India appears to have escaped the holiday effect.

Daily case numbers through the first six days of last week, Monday to Saturday, were: 31,182; 36,421; 35,414; 36,653; 36,212; and 36,439. That works out to a six-day average of 35,387. All these numbers are from the HT dashboard. The average is the lowest India has seen in four-and-a-half months. That would take us back to the third week of July.

These numbers lead to two interesting questions.

The first question is why did India not see the spike the US and countries in Europe saw after similar celebrations and gatherings?

The obvious answer — and because it is obvious there is also a strong likelihood of it being the wrong answer but more on this shortly — is that Diwali coincided with the end of the first wave of infections in India (or the beginning of the second), and because of this, it did not see a spike in cases two weeks later, despite people flouting social distancing norms or taking more risks by travelling.

This doesn’t add up because if nothing really changed in the virus’s ability to infect people (it didn’t; for instance, there wasn’t a sudden mutation that made it less virulent), and if people actually took more risks than they previously did, there should have been a spike in infections. This is exactly what happened in the US after Labor Day and which experts say is now happening after Thanksgiving. And this is exactly what happened in European countries.

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This suggests that the answer could lie in the chain of infection being broken more often and more easily than it was previously, and despite violations of social distancing norms — something that is possible only if the virus, as it seeks to jump from person to person, encounters more people who are immune to it. It’s difficult to say this for sure in the absence of regular, widespread tests for SARS-CoV-2 antibodies — blood tests that are popularly called sero-surveys — but the answer seems to lie in that direction.

The reason for the absence of a post-Diwali surge, then, could be a combination of two complementary factors: masking, social distancing and other safety protocols that some still followed (and continue to); and a relatively high level of exposure to the virus in the population, resulting in an equally high level of protection.

This is not to suggest that India has achieved herd immunity or is close to doing so. Nor is this an endorsement of any approach that focuses on achieving herd immunity. It is merely scientific conjecture that seeks to explain why India has not seen a post-Diwali surge.

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The second question (which, in some ways, derives from the first) is about the waves in which the coronavirus disease affects populations. We know that a wave starts waning when testing, tracing, and isolation start reducing the possibility of infection, and waxing as life returns to normal, as business and recreational and social activities increase, but there is also a natural trajectory to the infection. For instance, at a certain level of infection (or exposure), the number of new infections will start falling, gradually at first and then sharply. So, based on an understanding of these (the level of activity, and the infection rate), can one predict the timing of the next wave?

That is for the experts to answer.

Post Script: With India escaping the post-Diwali surge, if its current coronavirus disease trajectory stays in the plateau in which it finds itself till the end of the month, it is likely (a low but significant probability) that the second wave in India will be less intense — not just when compared to that in the US and Europe, but when compared to the country’s own first wave — because if all goes well, India could start vaccinating the people in the first of its six priority groups (prioritised in terms of when they will be administered the vaccine) early next year.