“SUTRA model” has flaws in predicting the pandemic – Scientists

What is the News?

The Indian government backed the SUTRA model to chart the Covid-19 trajectory in the country. But few scientists have raised concerns over the SUTRA model.

SUTRA Model:

• SUTRA stands for Susceptible, Undetected, Tested (positive) and Removed Approach.
• Purpose: SUTRA is a mathematical model. It is used for charting the trajectory of COVID-19 in the country.

Parameters: The model uses three main parameters to predict the course of the pandemic:

1. Beta or contact rate: This measures how many people an infected person infects per day. It is related to the R0 value. R0 is the number of people an infected person spreads the virus over the course of his/her infection.
   • For example, if a disease has an R0 of 18. Then a person who has the disease will transmit it to an average of 18 other people
2. Reach: It is a measure of the exposure level of the population to the pandemic.
3. Epsilon: It is the ratio of detected and undetected cases.

Why Scientists are calling the SUTRA model flawed?

• The SUTRA model predicted that the peak Covid-19 burden in India will be 0.6 million symptomatic infections by early 2021. Further, the model predicts fewer than 50,000 active cases from December. Thus, it creates a perception that the second wave of the pandemic was highly unlikely in India. But this is not true.
• The model relied on too many parameters. Also, these parameters got recalibrated whenever its predictions broke down.
• Further, the model was ‘calibrated’ incorrectly. It relied on a Sero Survey conducted by the ICMR in May 2020. The survey said 0.73% of India’s population may have been infected at that time.

What did the scientists working on the SUTRA model said?

• Scientists said that a mathematical model can only predict the future. That too will work as long as the virus dynamics and its transmissibility don’t change substantially over time.
• So the scientists said that is not the case with the Covid-19. The virus has been changing very rapidly. Hence, any prediction for Covid-19 must be continually readjusted.

Source: The Hindu