Coronavirus reproductive factor lowest in India, says new study amid swelling tally

Between April 6 and April 15 the infectivity rate has been estimated at 1.53 while on an average it has been 1.83 so far.

Published: 20th April 2020 02:16 AM  |   Last Updated: 20th April 2020 11:33 AM   |  A+A-

A police officer gives a sample for the rapid test at a camp during a government-imposed nationwide lockdown as a preventive measure against the coronavirus in Chennai Sunday April 19 2020. (Photo | PTI)

Express News Service

NEW DELHI: Even as India has now recorded over 15,000 COVID 19 cases, a study by the Institute of Mathematical Science has suggested that reproductive factor — the rate at which every infected person transmits the disease to others — could be one of the lowest in India, compared to most other countries.

The study also said that the extensive lockdown measures may not have been effective in the containment of the infection in Maharashtra but have been helpful in some states such as Tamil Nadu and Karnataka.

The reproductive factor or R0 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.

“The R0 for COVID global R nought for COVID 19 has been estimated between 1.5-4 and in India, it now stands at 1.83 which is towards the lower end of the spectrum,” Sitabhra Sinha, lead researcher of the paper ‘Epidemiological dynamics of the COVID19 pandemic in India: An interim assessment’ said.

Between April 6 and April 15 the infectivity rate has been estimated at 1.53 while on an average it has been 1.83 so far.

The researchers also discerned a significant deviation in the exponential rate of growth of the number of active cases in India beginning from April 6, approximately two weeks after the beginning of a nationwide lockdown put in place on March 24 as a containment measure.

“Given that up to two weeks following the beginning of the lockdown, we expect the growth of the number of active cases to primarily arises from infections which had happened prior to lockdown, it seems reasonable to attribute this deviation to the response of the epidemiological dynamics to the lockdown,” the researchers noted.

The study estimated that in the absence of the extensive lockdown imposed in the last week of March, the total number of active COVID-19 cases in India would have been in the range of 35,000-50,000 by April 20.

It, however, said that as the value of R0 is substantially greater than 1 in the country, this suggests that in the absence of other containment measures, a lockdown by itself may be insufficient to prevent the epidemic from growing once the restrictions are removed.

The paper also analysed the number of active cases from those states where the epidemic has resulted in a large number of infections and found large variations in the nature of the growth of the number of active cases in different states.

While, Maharasthra, which has the highest number of active cases, showed an exponential growth curve similar to that for the country as a whole, the effective reproduction rate estimated for the period April 4-15 was 1.7 — lower than the value of R0 estimated for India, but significantly higher than the value of R measured for India over the same time. 

“Unlike that seen in the nation-level data, there is no discernible effect of the lockdown in the data for the state,” noted the researchers.

“States such as  Tamil Nadu and Karnataka, show a linear trend for growth of cases instead of an exponential nature — suggesting the epidemic may have been contained in these states.”

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