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New Delhi: India’s effective reproduction number (R) — an indicator of how fast the infection is spreading — has reduced to 1.16 this week from 1.31 last week.

R is an estimate of the number of people one Covid patient can infect. Even though India’s active cases continue to increase, a reduction in R indicates that the infection is spreading slower than before.

The R value for India had been increasing since January. However, the current R of 1.16 is the lowest since around 19 March, when it was 1.19.

As of Monday, India has 34,13,642 active cases of Covid-19. R needs to be below 1 for active cases to come down.

Graphic: Ramandeep Kaur | ThePrint

Sitabhra Sinha, a researcher at the Institute of Mathematical Sciences in Chennai, who has been tracking the R values since the beginning of the pandemic said the data shows there has been an improvement in the Covid-19 situation in terms of the growth rate — both at the national level as well as in most states with a high burden of active cases.

Impact of state lockdowns

The drop may have come primarily due to a fall in Maharashtra’s R value. Since the state has the highest proportion of active cases, India’s overall R values mirror the peaks and troughs of Maharashtra’s Covid wave.

The lockdown in the state has helped bring its R value to below 1.

Graphic: Ramandeep Kaur | ThePrint

Delhi, where the healthcare system has been overwhelmed by the surge in cases and hospitalisations, too saw a drop in its R from 1.6 last week to slightly over 1 this week. The city too has been under lockdown since 19 April.

Graphic: Ramandeep Kaur | ThePrint

Other states

Karnataka, which currently has the second highest burden of active cases, saw an increase in its R from 1.40 last week to 1.43. The state announced a 14-day lockdown from 27 April. The effects of such measures are expected to show up after about two weeks.

Rajasthan and Uttarakhand, among the high burden states in the country, currently have the highest R values of 1.54 and 1.51, respectively, although both have seen a reduction in their R from the previous week.

This is followed by Gujarat, where R has dropped to 1.48 from 1.55 last week. Haryana too saw a decrease in its R from 1.50 last week to 1.37.

Bihar, which until two weeks ago had one of the highest R values in India at 1.92, saw R drop to 1.21. The state’s R last week was 1.62. Similarly, Jharkhand’s R fell to 1.21 from 1.5 last week. Two weeks back, the state had an R value of 1.72.

Graphic: Ramandeep Kaur | ThePrint

With the reduction in R in Maharashtra, the adjoining state of Chhattisgarh has also seen its R drop to below 1. Two weeks back, the state’s R was 1.56, which reduced to 0.93 last week. Now the value is 0.94.

Both Uttar Pradesh and West Bengal now have R values very close to 1, but the data from the respective states is not robust enough for an accurate estimate, Sinha said.

Major cities

Among cities, Bengaluru currently has the highest R of 1.42 — same as last week. Kolkata, where R was 1.48 last week, saw the value reduce to 1.19 this week.

Graphic: Ramandeep Kaur | ThePrint

The effect of the lockdown has also benefitted Mumbai, where R has been below 1 for the last three weeks. Currently Mumbai’s R is 0.84. However, R in Pune is still a little over 1, although the value has decreased from last week’s 1.13.

In Chennai, R reduced to nearly 1 from 1.39 last week. Kolkata has R at 1.19 from 1.48 last week.

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