NEW DELHI: A statistical analysis of active cases of COVID-19 has revealed a significant decline in reproductive numbers of SARS CoV 2 -- the virus behind the COVID 19 epidemic -- in India, possibly due to the nationwide lockdown and social distancing measures.
R0 -- pronounced R-naught and known also as the basic reproductive number -- refers to how many other people will catch the disease from a single infected person, in a population that hasn’t been exposed to the disease before. If R0 is below one, the epidemic eventually dies out. Above one, it keeps growing, possibly exponentially.
An analysis by the Institute of Mathematical Sciences, Chennai, has shown that R0 for novel corona virus was 1.83 from March 5 to Apr 5 in India but dipped to 1.53 from April 6 to April 13.
Globally, R0 for SARS CoV 2 has been estimated between 2 and 4 and scientists believe that the factor varies from place to place.
“The close analysis of R0 graph pattern suggests that there has been a statistically significant lowering of the rate at which the number of cases has been growing,” said Sitabhra Sinha who led the analysis.
“Assuming that this is a genuine new trend, I guess we can attribute this to the lockdown, as in any case, we were expecting the response to the lockdown to be manifested after about two weeks -- this is because for the first two weeks of the lockdown period, the increase in numbers would be mostly due to people who had gotten infected before the start of the lockdown,” he said.
Sinha added that a closer look at the individual states shows that the picture is more complex.
“First of all, since the data does not cover the entire country, the estimation is less robust. Secondly, while a few states like Telangana do seem to be showing a similar kind of reduction in the growth rate starting from April 6 -- consistent with what we see nationally --, we still don't see such a reduction in the data from Maharashtra, currently the number 1 in terms of active cases,” he added.
The researcher added that both Tamil Nadu and Kerala are showing linear, rather than exponential trends, suggesting that the epidemic is spreading at a far slower rate than expected during an epidemic.
The analysis by the IMSc coincides with a report on India’s 21-day lockdown by the Centre for Disease Dynamics and Policy, Johns Hopkins University and Princeton University in which researchers modeled the impact of the 21-day lockdown on the spread of COVID-19 in India in March and April; before, during, and after the lockdown is lifted.
"India has implemented a nationwide 21-day lockdown, which is predicted to avert a large number of COVID-19 infections in the short term, although it is unknown how the outbreak will unfold once the lockdown is lifted," noted the report.