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Explained: R-value over 1 in big cities, likely start of third wave

Covid-19 omicron numbers explained: The sharpest increases in cases are being seen in the major cities — Delhi, Mumbai, Bengaluru, Pune, Kolkata, Chennai and others.

Written by Amitabh Sinha | Pune |
Updated: December 31, 2021 10:23:32 am
coronavirus india, coronavirus omicron india, omicron variant cases in india, new variant omicron symptoms, coronavirus omicron india latest update, omicron virus india, coronavirus vaccine statistics, current affairs, current affairs news, Indian expressCommuters board a crowded bus in Mumbai. (Express photo by Amit Chakravarty)

Although the government has not described it as such, there are now unmistakable signs that India has entered the third wave of the Covid-19 pandemic. The surge in cases that has started is unlikely to subside or change course over the next few days.

But it is too early to say anything about the magnitude or the quality of this surge. It need not be similar to the first two waves that the country has witnessed so far, or follow the trajectories seen in some of the other countries in Europe or in the United States. South Africa is following a very different trajectory, and so, it seems as of now, is Germany. In both these countries, cases seem to be stabilising, though it is not over yet, and part of the puzzle could also be related to inconsistent reporting of data during Christmas break.

Not surprisingly, the sharpest increases in cases are being seen in the major cities — Delhi, Mumbai, Bengaluru, Pune, Kolkata, Chennai and others. This is not just because of their large, and concentrated, populations, but also due to the fact that these get the maximum number of incoming foreign travellers. The Omicron variant, which is the reason for the current surge, would first begin circulating in these populations before moving to the interior. These are also the places with better, and more prompt, testing infrastructure.

The reproduction number or R, an indicator of how quickly a disease is spreading in the population, has crossed 1 in all these megacities, according to the latest analysis by a group of researchers, led by Sitabhra Sinha, at the Chennai-based Institute of Mathematical Sciences. An R-value of 1, which signifies that every infected person is passing on the infection to at least one person on an average, is a key threshold after which cases begin to rise rapidly. Both Delhi and Mumbai have R-values over 2 right now, according to Sinha’s analysis, indicating that in both these cities, one person is transmitting to more than two people on an average. This is a forecast for a very quick rise in cases in both these cities.

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A major reason for the unprecedented surge in Europe and the United States is the fact that it came during the annual festival season when large gatherings are the norm. And while many governments have announced some restrictions to control the surge, they have largely been reluctant to spoil the Christmas or New Year celebrations or gatherings. There is no such compulsion in India right now, and if people do follow Covid-appropriate behaviour in a responsible manner, it is possible for the country to negotiate this wave with minimal economic disruption.

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