BENGALURU: In the tidal wave of surging SARS-CoV-2 infections, an unprecedented high R-Value has taken scientists by surprise. The R-Value, or reproduction number, measures the contagiousness of the disease in terms of the mean number of individuals who will get infected by a single infected person. So, if the R-Value is two, then on average, one infected person will infect two people.
“The R-Value in the current wave is very high in some states, in comparison to the first and second waves. This is unusual and surprising. We have analysed data and found that the R-Value in many states is ranging from 2 to 6, which is very high. This also shows that the infection has spread beyond the metros, into the country’s hinterland,” Dr. Sitabhra Sinha of the Institute of Mathematical Sciences (IMSc) in Chennai, who is leading the data study of the SARS-CoV-2 virus in India since the onset of the pandemic, told TNIE.
The data is being collected from crowdsource initiative www.incovid19.org which is continuing the Covid-19 India initiative. The latter had stopped updating its database from October 31 last year.
Sinha said that major metros have been showing R-Value greater than one since mid-October 2021. “The surprise is that states like Bihar, Uttar Pradesh, Jharkhand, Gujarat and Haryana, in a coordinated manner, have been recording high R-Value since the last week of December,” he added.
“In Gujarat, on December 1 last year, the R-Value was greater than 1 even though the actual number of active cases was less than 1,000. From December 24, the R-Value had climbed to 3. In Jharkhand, the values have been fluctuating. Between December 14 and 19, the R-Value in the state was 1.2. It rose to 2.09 between December 20 and 25. Between December 26 and January 2, it rose to 5.38. In UP, the R-Value shot up to 4.36 from December 28. In Delhi, the R-Value has been above 1 from November 30. On December 26, it went up to 4.6,” said Sinha.
He said there could be three reasons behind the sharp increase in R-Value across the country. “It could be because of the waning of antibodies in people, who had taken the vaccination early last year. Secondly, the ability of this pathogen to escape immune response in people previously exposed to it, and thirdly, the churning of the population that has allowed a new group of susceptible people to be exposed to it,” said Sinha.
He said the high R-Value and sudden surge in Covid-19 cases has posed a challenge to understand and predict the stage of the current wave that India is currently in. “If the susceptible population is less, then the rapid growth in the number of infections would be quickly arrested and fall subsequently. If people have been infected before and are getting re-infected, it may stay on for a while. A lot depends on the action taken on the ground. The pandemic will end but we cannot let nature take its course,” said Sinha.