India's Covid-19 transmission rate has increased for the first time since March, a new study by the Institute of Mathematical Sciences in Chennai shows.
The coronavirus reproduction number or R estimates the number of people infected by an already infected person. In India, R was decreasing from 1.83 for months since March 4 but has shown a spike in the first week of July, which marks the second unlocking phase, a report by Indian Express states.
Authorities want the reproduction number to reach 1, as it signals the flattening of Covid-19 curve. The R is currently at 1.19, which signifies that on an average, one infected person is spreading the disease to 1.19 people more, said Dr Sitabhra Sinha from the institute.
According to Sinha, it takes about 10 days to two weeks for any effect to show up as increased or decreased case numbers. This is the reason she believes the increase which is being witnessed now has its origin in events that took place during mid-June or slightly later.
She said the bottom line was that India was now in the situation that it was in May and early June, and that the further decrease witnessed in late June was neither sustained nor improved upon, the report mentions.
Some states are faring better, though. Delhi, from an R number of 1.25 between June 13 to 16 is now witnessing an R of around 1. The capital city, for a few days from June 21 witnessed an R slightly above one. Sinha said the curve was "sub-exponential" which means that it has not been growing exponentially for a while. Haryana too, is showing a similar pattern.
When Tamil Nadu flattened the curve substantially is the only other time that a state with many cases exhibited such positive trends.
In March, coronavirus R number was 1.83 in India, while the rate was 2.14 in Wuhan and 2.73 in Italy. India's R dropped to 1.55 between April 6 and 11 and subsequently dropped further to 1.49 and then 1.2 by the beginning of June amid phased lockdown relaxation.
The transmission rate continued to decrease into June, reaching 1.11 by June 26, the report states. The transmission rate has now picked up between July 2 and 5 to 1.19, after a month of unlocking.
Karnataka, Telangana, Andhra Pradesh have the highest R numbers - 1.66, 1.65 and 1.32, respectively.
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States which were previously registering a fast spike in cases have slowed down; Gujarat is at 1.15 transmission number while West Bengal at 1.1. Sinha said that the current increase in R can be attributed to the high R in some southern states.
Sinha added that states like Assam and Rajasthan were not consistent enough for an R number to be estimated. According to her modelling, total active Covid-19 cases could reach 6 lakh by the month's end. While Maharashtra could report over 1.5 lakh active cases by July 21, Tamil Nadu could witness 1 lakh.