Sutra Model

SUTRA is Susceptible, Undetected, Tested (positive) and Removed Approach. SUTRA Model  is used to chart the trajectory of COVID-19. It is used to predict the future of COVID-19 infections, susceptibility, undetected and positive persons in the country.

• This SUTRA Model is backed by GoI and was developed by professors from IIT Kanpur, IIT Hyderabad.

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

1. 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.
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.

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Issues with SUTRA

• There have been many instances of the SUTRA forecasts being far out of bounds of the actual caseload and the predictions of the SUTRA model are too variable to guide government policy.
• The SUTRA model was problematic as it relied on too many parameters, and recalibrated those parameters whenever its predictions “broke down”.
• The SUTRA model’s omission of the importance of the behaviour of the virus; the fact that some people were bigger transmitters of the virus than others (say a barber or a receptionist more than someone who worked from home); a lack of accounting for social or geographic heterogeneity and not stratifying the population by ageas it didn’t account for contacts between different age groups also undermined its validity.
• New variants showed up in the SUTRA model as an increase in value of parameters called ‘beta’ (that estimated contact rate).