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Decline in India’s Covid R0 and how effective is the ‘test, test, test’ mantra

In episode 450 of #CutTheClutter, Shekhar Gupta explains if the 'test, test, test' mantra applies to India and analyses testing in different countries to investigate its effectiveness.

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New Delhi: According to a new report, the reproduction number or R-naught (R0) of Covid-19 in India is now 1.36.

R0 indicates the number of people a patient can directly infect in a healthy population. The higher the R0, the faster an epidemic spreads. It had started with 1.7, then was estimated at 4 on 23 May and then came down to 1.3 or 1.4. The last count was 1.55, and now it is 1.36. This indicates that there has been a consistent decline in the reproduction rate.

Also read: India’s Covid-19 R0 down to 1.36 now, 25,000 cases by April-end at this rate: IMS scientist

Test, test and test

Dr Srinath Reddy, President of the Public Health Foundation of India, in an interview with The Financial Express, said that population-wide testing is neither feasible nor advisable. Dr Reddy has formerly headed the Department of Cardiology at All India Institute of Medical Sciences (AIIMS) and is a member of the executive group of the International Steering Committee of WHO’s COVID-19 Solidarity trial.

WHO Director-General Dr Tedros Adhanom Ghebreyesus had asked countries to ‘test, test and test’ to defeat Covid-19 and since then, this strategy has become popular wisdom. Dr Reddy said more tests are good, but not in isolation, and other things also matter. He pointed out the example of Bolivia and Belgium. Bolivia has only conducted 2.4 per cent of the tests conducted in Belgium, but only 34 people have died of Covid-19 in Bolivia whereas close to 6000 in Belgium. Both Belgium and Bolivia have a population of 1.16 crore.

Dr Reddy gave the example of recovered patients who have tested positive again in South Korea. False positives and negatives will cause a great deal of confusion, he added.

He suggested that India should continue with its strategy of testing suspected cases and said people with influenza-like symptoms could also be tested as testing is ramped up.

Watch the latest episode of CTC here:

Also read: Covid-19 fight is a Test match, not a T20. Here’s what India needs to do to win


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  1. Please take into account population density of the Belgium (991 people per square mile) and Bolivia (28 people per square mile).

  2. I agree. I think people who say ‘test test test’, dont understand the basics of sampling strategy. But these days every man and his dog is a expert.

  3. Koreans know that people get re-infected because they TESTED for infection.
    False positive and False Negative – come out of testing not hypothesis and predictive values are based on prevalence of disease- which again is a function of testing.
    One can not say there is no community transmission because our data is not sufficient to prove it, then quote the same data to say the rates are going down or flattening.
    What we are doing is – divide a second into a millionth part ( that is easy and theoretical) and then use Gnome and its shadow to predict time.

    • As I said. Confusing prediction with hypotheses and sampling. Actually, testing using response driven sampling (RDS) (which most epidemiologists do) is biased upwards.

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