NEW DELHI: A statistical analysis of active coronavirus cases has revealed a significant decline in reproductive number of SARS CoV 2 virus in India, possibly due to the lockdown and social distancing.
The factor to arrive at how many people could catch a disease from a single infected person in a population that hasn’t been exposed to the disease before, is R0, also called R-naught. If R0 is below one, the epidemic eventually would die out. Above one, it keeps growing, possibly exponentially.
An analysis by the Institute of Mathematical Sciences, Chennai showed that R0 for the novel coronavirus was 1.83 from March 5 to April 5 in India but dipped to 1.53 from April 6 to April 13. Globally, R0 for SARS CoV 2 has been between 2 and 4.“A close analysis of the 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 team of analysts.
“Assuming this is a genuine new trend, I guess we can attribute it to the lockdown, as in any case we were expecting the response to the lockdown to be manifested after about two weeks from its beginning. 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. “While a few states like Telangana do seem to be showing a similar kind of reduction in the growth rate starting April 6, which is consistent with what we see nationally, there is no such reduction in the data from Maharashtra,” he added.
‘Linear trend in TN, Kerala seen’
The researcher added that both Tamil Nadu and Kerala are showing linear, rather than exponential trends, suggesting the epidemic is spreading at a far slower rate than expected. The analysis by the IMSc coincides with a report 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’s 21-day lockdown 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.