In a huge country like India, elements used to arrive at a number change frequently.

New DELHI: Multiple Covid-19 epidemiological models, predicting fatalities and the number of infected in India, had come into existence in the initial days of February and March, giving a grim prediction of the future.
However, more than a month of the lockdown period later, the reality shows a different picture viz-a-viz the predictions that were made by these models. Such epidemiological models, projections and predictions are used by the government in formulating critical policy decisions. When Prime Minister Narendra Modi had announced a nationwide lockdown, effective from 12.01 am, 25 March, the number of Covid-19 cases in India was less than 700.
Centre for Diseases Dynamics,Economics and Policy study
One of the early predictions that conducted by the Centre for Diseases Dynamics, Economics and Policy (CDDEP), in Washington and New Delhi, was published on 24 March. This study took into account the demography (age, gender) of the Indian population, socio-economic characteristics and access to healthcare to arrive at its predictions.
The researchers at the CDDEP predicted that between 25 March and 25 August, India could potentially see around 2 to 2.5 crore people being affected by the coronavirus. The peak of the infection, predicted by the researchers at CDDEP, will be between 25 April 25 to 5 May whereby about 2,500 people per lakh of population would be getting affected.
The researchers gave three scenarios— one with the high trajectory where the effect of lockdown would potentially not be giving any results and that there would be a rapid spread of the disease where more than 2.5 crore people in India would be affected by May.
The medium scenario, according to the researchers, would be where there would be no affect of the lockdown, temperature or humidity. In this case, the CDDEP researchers predicted that about 2 crore people in India would be affected by the virus and the peak of the cases in India would be somewhere near 25 May.
In the low case scenario, which the researchers called “optimistic scenario”, with decreased transmission and temperature and humidity playing its role, the total number of Indians getting affected could be around 1-1.3 crore people and in this case, the peak is predicted to come around 25 June.
These total number of cases predicted by CDDEP researchers include asymptomatic, symptomatic as well as hospitalised cases.
Their next study, published on 20 April, stated that the national lockdown had brought time to the officials to ramp up infrastructure and has thus delayed the peak while giving four different scenarios.
The study stated: With hard lockdown continuing along with social distancing norms followed strictly along with isolation of cases, India could see a peak infection of about 9 crore Indians getting affected by July this year, which would include asymptomatic, symptomatic and hospitalised patients (long-term reduction in transmission reduces peak infections.)
With only a hard lockdown, the peak of infection in India would see about 13 crore Indians getting infected and the peak will be somewhere around 10 June. Even with a moderate lockdown, India would witness about 13 crore peak infections with the peak coming around 3 June. With no intervention, post the 21-day lockdown, India could see a peak infection coming around 16 crore people by 20 May. In effect, their best case scenario, as per the latest study, is 9 crore Indians would be affected, while in the worst case scenario, 16 crore would be.
Cambridge model
In the “Cambridge Model” that was developed by Cambridge scholars Rajesh Singh and R. Adhikari, the two scholars used SIR model (Susceptible-Infected-Removed). This Cambridge model used Indian homes as a channel of social transmission as three generations of family live in one home.
This model, published on 26 March, has predicted four scenarios. In the first case, the study said that a meagre 21-day lockdown would not yield any results and that cases would start to peak after the 21-day lockdown is lifted. The Cambridge model suggested that even during the lockdown, India is likely to witness more than 2,700 deaths.
Study facilitated by K. Vijayaraghavan, Principal Scientific Advisor to the Government of India
In the latest of such study that was published earlier this week, in the worst-case scenario, Covid-19 mortality in India is projected to increase to 38,220, while the number of positive patients is predicted to touch nearly 30 lakh.
These projections were based on a statistical model “Covid-19 Med Inventory” that was prepared by experts from the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Indian Institute of Science-Bangalore, IIT-Bombay and Armed Forces Medical College-Pune and facilitated by K. Vijayaraghavan, Principal Scientific Advisor (PSA) to the Government of India.
ICMR study
The Indian Council of Medical Research (ICMR), too, had published a study predicting the spread of Covid-19 in the country. The study titled “Prudent public health intervention strategies to control the coronavirus disease 2019 transmission in India: A mathematical model-based approach”, was published in the IJMR (Indian Journal of Medical Research) on 24 March. However, very curioulsy, the study has now been removed from the website and is only available to those who were able to download it.
While the study has not given any real numbers as to how many would be affected in the best and the worst case scenarios, it has suggested that between 1% and 10% of the population will be infected at the peak of the epidemic, depending on its severity.
According to the study, in the optimistic case, 150 people per 10,000 would be impacted in Delhi without intervention, while in the pessimistic scenario, it would go to 1,000 infected per 10,000. While taking government intervention into account, it stated that in the best case scenario, the number of infected in Delhi would be roughly 20 per 10,000, while in the pessimistic case, it would be almost 1,000 per 10,000.
Covid 19 study group report
A report released on 22 March by the “Covind-19 study group” comprising 14 experts from Johns Hopkins University, University of Michigan, University of Connecticut and Delhi School of Economics, stated that if a nationwide intervention is put, the number of Covid cases in India will be 13,800 cases which rise to 22 lakh cases by 15 May if there is no intervention.
Study by G. B. Pant Engineering College, Delhi and Chitkara University, Punjab
As per a prediction done by experts from G.B. Pant Engineering College, Delhi, and Chitkara University, Punjab, India is likely to have nearly a million confirmed cases by the end of May 2020.
The model predicted that Covid-19 would be at its peak between the third and fourth weeks of April 2020 in India. The total number of predicted confirmed cases of Covid-19 might reach around 68,978, and the number of deaths due to Covid-19 is predicted to be 1,557 around 25 April 2020 in India.
Other studies
On 23 March a study that was published on an online publication platform, Medium, which was authored by an Indian doctor, used the SEIR model (Susceptible, Exposed, Infectious, Recovered) to predict the number of infected and the number of deaths in India due to Covid-19. This same model was used to predict SARS cases.
The author arrived at a conclusion that if there was no intervention from the government, like lockdown, the number of infected in India would be around 115 crore or almost 80% of the total population of the country being affected by Covid-19. The study further stated that without intervention, the number of deaths in India could have been around 4.5 crore  in a span of six months. That was the worst case scenario.
The best case scenario stated that the maximum number of infected would be around 13,000 infected persons, with 300 deaths.
The use of using numerical modelling to map the expected fatality and spread of an infectious disease goes back centuries. One of the first attempts was made by 18th century mathematician Daniel Bernoulli, who tried to map the spread of smallpox.
However, they have rarely been accurate as too many elements are involved, especially in a country as huge as India, where the elements that are used to arrive at a number, change frequently.
On 7 April, Robert Redfield, the Director of the Centers for Disease Control, US, perhaps summed the situation the best when he said, “I think you’re going to see the numbers are, in fact, going to be much less than what would have been predicted by the models,” he said.

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