What is the mathematical modelling of COVID-19 by Indian National Supermodel Committee?

Recently, the Indian National Supermodel Committee has announced that India passed its 'COVID-19 peak' in the month of September 2020 and the active cases are likely to fall to a 'minimal' level by February 2021. These predictions are arrived at with the help of a mathematical model. 

In May 2020, the Department of Science and Technology (DST) constituted the Indian National Supermodel Committee consisting of mathematicians, computer scientists and medical professionals to track the evolution of the ongoing COVID-19 pandemic in the country and to recommend future policy interventions.  

How did the scientists conclude the predictions?

The scientists arrived at these predictions with the help of mathematical modelling. In the absence of cold numbers, they drew assumptions on how quickly the disease spreads, the varying susceptibility of adults as opposed to children and so forth. 

Susceptible-infected-recovered (SIR) model is one such model used by the scientists for drawing conclusions. In this model, the population of the country is divided into three groups, namely, Susceptible, Infectious, and Recovered. The model assumes that an individual in a defined population will be a part of any of these groups at any given point of time. However, the number of people in each group changes over time. 

At the beginning of the pandemic, 'Susceptible' group has the highest number of people while the 'Infectious' group has the lowest number of people. As the pandemic advance, the number of people in the 'Susceptible' group decreases while the number in the 'Infectious' group increases.

What are the key findings of the paper? 

Although the modelling committee was constituted of seven members, the scientific paper published in the Indian Journal of Medical Research has only three authors — a physician, a mathematician and a computer scientist.

1- On 25 March 2020, the first nationwide lockdown in India came into effect. 

2- The paper hypothesised that in the absence of a lockdown, the active COVID-19 cases in the country would have crossed 14 million and the peak would have arrived by the mid-May. 

3- India would have witnessed more than 2 million deaths in the absence of a lockdown. 

4- The number of deaths in India with current trends is projected to be less than 0.2 million. 

5- The report also stated that in the absence of subsequent lockdowns in the month of April and May, India would have witnessed a peak between 0 and 5 million active infections and would have witnessed 0.5-1 million deaths. 

6- The major limitation of this model was the non-availability of accurate data and the data was crowd-sourced by 'covid19india.org'.

Predictions of other mathematical models:

The United Kingdom did not impose travel restrictions except on the elderly, letting the virus through the population in order to acquire 'herd immunity'. However, a report based on the epidemiological model stated that with such a policy, one in two people in the country would die. Soon after this prediction, the policy in the United Kingdom changed. 

In April 2020, India estimated that the pandemic would die out by May 2020 on the basis of the rudimentary model but this isn't the case. 

The announcement of India having passed its peak of active COVID-19 cases comes after national caseload started declining. In early September, around 90,000 active COVID-19 cases were reported daily which have now decreased to around 55,000 cases daily. 

The officials of the Ministry of Health, Government of India have not been committal about India passing its COVID-19 peak but have admitted that the mathematical models are helpful in terms of planning. 

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