Covid R-value rises amid threat of third wave: All you need to know

As states across India race to control the spread of the coronavirus disease (Covid-19) ahead of an expected third wave in October, there is a more worrying factor in the form of rising R-value. The R-value in the last week of August rise to 1.17 as against 0.89 between August 14-17, according to the researchers at the Institute of Mathematical Sciences, Chennai.

The R-value determines how rapidly the Covid-19 pandemic is spreading.

"Not only is it greater than one, it is much higher than the last time there was a scare of a third wave (it was 1.03 at that time)," Sitabhra Sinha, who is leading the team of researchers, told news agency PTI.

"This is driven by several states having their R-value go over 1 in the last few days of August - most notably Kerala and Maharashtra, but also Mizoram and Jammu and Kashmir," Singh added.

Why is R-value important?

The Reproduction number or R denotes how fast an infection is spreading. When a wave is at its peak, it is evident that the virus is spreading at a faster rate. But at a time when the wave is receding, a slight increase of R-value can indicate an impending upward trend in the wave again.

If R is greater than 1, the number of infected people is increasing in each round - this is what is called the epidemic phase. In other words, it tells how 'efficiently' a virus is spreading.

States with highest R-value

The R-value of Kerala stood at 1.33, which is the highest number of active cases in the country, according to the Institute of Mathematical Sciences. It was 1.36 for Mizoram, 1.25 for Jammu and Kashmir, 1.09 for Andhra Pradesh and 1.06 for Maharashtra.

R-value during the second wave

When the second wave swept through the country between March to May, the R-value was 1.37 (between March 9 to April 21).

From May 15-June 26, the R-value stood at 0.78. However, it slowly started increasing - it was 0.88 from June 20-July 7, 0.95 from July 3-22, 0.96 from July 24-27.

It breached the value of 1.03 for the first time after the second wave during July 27-31. However, since then it has slowly started to decline.

The R-value was 0.92 from August 6-9, and rose to 0.99 between August 12-14. But it slipped to 0.89 between August 14-17.