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Why in news?

  • SUTRA model has been used by the Government of India to fight the second wave of COVID 19 pandemic.
  • The prediction for the second wave, however failed and the rising number of cases are a standing proof of the same.
  • The second wave of Covid-19 has claimed thousands of lives since April 2021.

What is SUTRA model?

  • SUTRA (Susceptible, Undetected, Tested (positive), and Removed Approach) first came into public attention when one of its expert members announced in October that India was “past its peak”.
  • The model uses three main parameters to predict the course of the pandemic which are:
    • Beta: Also called contact rate, which measures how many people an infected person infects per day. It is related to the R0 value, which is the number of people an infected person spreads the virus to over the course of their infection.
    • Reach: It is a measure of the exposure level of the population to the pandemic.
    • Epsilon: It is the ratio of detected and undetected cases.

Issues With The Model

  • The panel said that their predictions were wrong as the nature of the virus has been changing constantly and very rapidly.
  • As per the committee,” In such a context, any prediction for Covid-19 must be continually readjusted, sometimes almost daily.”
  • Various epidemiological models extrapolate cases on the basis of
    • Data of the existing cases
    • Behaviour of the virus
    • The way of its spread
    • However, the SUTRA model chose a data centric approach.
  • The equation to find out the estimates of future infections and the timing of a peak occurring, require certain ‘constants’. Such numbers on the other hand kept changing and their values depended on the number of infections reported at various intervals.
  • So any equation cannot make it clear when a constant changes. An increase in the number of cases thus couldn’t be predicted in advance.
  • Others are of the view that SUTRA relied on many parameters and recalibrated them when its predictions broke down.
  • Also many scientists are of the view that the exponential rise was not calculated as there was a contact between people and populations went wrong every time.
  • It was assumed that the best it could do was go upto the pre lockdown values. No one thought about the new strains that could come up with time.
  • The model also relied on the ICMR in May that said that 0.73% of India may have been infected at that time. However, the results of the first survey had not been correct.

Way Forward

  • The new variants have been put up in the SUTRA model as an increase in value of parameters called beta.
  • As per the scientists now “the model is observing changes in parameter values.
  • It does not care about what is the reason behind the change. And computing new beta value is good enough for the model to predict the new trajectory well.”
  • Due to the combination of epidemiologists, data-centric modelling such as SUTRA and time-series models can work to their best.


Mussoorie Times

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