A mathematical term, R-value is used to track the Covid-19 virus and understand its spread in a given geographical area. It indicates the virus’ rate of reproduction.
Covid-19 cases have been witnessing a sudden surge in Delhi, with the capital city reporting 1,042 fresh Covid-19 cases in the last update. The spike in cases indicates that the city’s R-value (reproductive value) has been recorded at 2.1 this week, according to an analysis done by IIT-Madras.
A few days back, India’s R-value crossed 1, for the first time since mid-January, during the third wave of the pandemic.
The country's R-value, steadily increasing over the last few weeks, is 1.07 for the week between April 12-18. In the preceding April 5-11 week, it was 0.93. The last time the R-value was above 1 was in the week between January 16-22, when the value was 1.28.
A mathematical term, R-value is used to track the Covid-19 virus and understand its spread in a given geographical area. It indicates the virus’ rate of reproduction
‘R’ stands for the number of people one person can infect. Hence, if the R-value is 1, that means, every infected person will infect another person. And when the R-value goes up, that means the number of people, likely to be infected, increases.
When the R-value goes below 1, then there are chances that the outbreak will halt as there are not too many people, who are likely to be infected.
Commenting on the uncertainty, of whether Delhi will be witnessing the fourth wave due to an increased R-value, Dr Jayant Jha, Assistant Professor, Department of Mathematics, IIT-Madras said that it is too early to make any such estimation.
“We can only say right now that every person is affecting two others....but we need to wait a bit to declare onset...we don't know about the immunity status and whether the people who got affected during the third wave in January are getting affected or not again," he said.
According to various media reports, the Omicron sub-lineage has been detected in most samples collected in Delhi in the first fortnight of April along with Omicron variant derivative BA.2.12.1 and that could be a possible reason behind the sudden surge in Covid-19 cases in the national capital.
"It is interesting that the major cities of Mumbai, Chennai and Bengaluru also have R above 1, suggesting that urban areas may be showing an increasing number of cases even though at the level of the entire state such an increase may not yet be apparent,” experts say.
Delhi and Uttar Pradesh have an R-value above 2. Data for Kolkata was not available, Sinha said.
The estimated R-value in the week ending April 18 is 2.12 for Delhi, 2.12 for Uttar Pradesh, 1.04 for Karnataka, 1.70 for Haryana, 1.13 for Mumbai, 1.18 for Chennai and 1.04 for Bengaluru.
Among the major states, Kerala and Maharashtra have an R-value less than 1, with values of 0.72 and 0.88 respectively.
Karnataka also has R over 1 currently, possibly because of the rising cases in Bengaluru.
(with inputs from PTI)