Sitting in homes due to lockdown forced by novel coronavirus pandemic, millions of people in India and across the world have this question on top of their mind: when will Covid-19 end? Researchers in Singapore have risked answering this question.

On the basis of the pattern of spread of Covid-19 from China to the rest of the world and slowing down, the researchers in Singapore have a predicted date for 131 countries each when novel coronavirus outbreak will end there.

Covid-19 will end in India around May 21-22, the researchers said. This is the time when novel coronavirus infection will be 97 per cent down compared to April 20, which they found as the turning date.

This is close to what the Indian Council for Medical Research (ICMR) hinted last week. ICMR director Dr Balram Bhargava had said, "One can say we have been able to flatten the curve."

The ICMR said the positivity rate has been stable at around 4.5 per cent in India in recent weeks. This stable rate of spread of Covid-19 could be a signal of India having passed the turning date, estimated by the Singaporean researchers.

Their mathematical model predicts that by June 1, India will have cured 99 per cent of Covid-19 cases. And, the novel coronavirus will be eliminated by July 26 from India, the researchers estimated.

This will, however, sounds optimistic given the scale of the surge in big Indian states and cities - Mumbai and Pune in Maharashtra, Delhi, Jaipur in Rajasthan and Indore in Madhya Pradesh among others. On the other hand, four states though smaller in size of the population -- Goa, Tripura, Manipur and Arunachal Pradesh -- have become free of Covid-19.

However, there is strong corroboration for the model, called the SIR (susceptible-infected-recovered) model. It estimated February 8 to be turning date for China, and February 27 as End-97 per cent date.

On the ground, China on February 19 reported the lowest number of fresh coronavirus infection in a month, indicated that the country was past the turning date.

The SIR model had March 4 as End-99 per cent date for China, which on March 7 reported 99 fresh Covid-19 cases, the first below 100 daily cases since the outbreak.

April 9 was End-100 per cent date for China. It has not happened in a strict sense of the term as China continues to report new cases. But, it was on April 8 that China allowed people to leave Wuhan, the Covid-19 ground zero, for the first time since it enforced lockdown in January.

Also, China has said that almost all the new Covid-19 cases in recent weeks are imported. On April 25, China said it recorded just one local novel coronavirus infection case in 10 days. Others were imported Covid-19 cases.

The SIR model is very close to the ground situation in China. This research prediction brings some hope for Indians.

However, the researchers have themselves warned that "the model behind our prediction is only theoretically suitable for one-stage epidemic. The prediction is also conditioned by the quality of the data."

According to this mathematical model, Covid-19 will end in early December this year.

But this does not come without a note of caution. "The reality is the future is always uncertain. No one predicted the Covid-19 outbreak in October or November 2019, although Bill Gates famously warned about the potential damage of a global infectious disease to the world during a TED Talk in 2015," Jianxi Luo, the writer of the research paper said.