Almost a million people in the suburbs of Wuhan, where the coronavirus pandemic broke out, were placed in isolation after the discovery of only 4 asymptomatic cases of Covid-19 infection, the BBC reports.

Residents of Jiangxia District were ordered to stay at home for three days after the discovery of 4 cases.

China continues to pursue a so-called “zero-covid” strategy, calling for mass testing, strict isolation rules and city-wide quarantines.

This resulted in significantly fewer deaths than in many other countries.

But that strategy faces growing opposition as people and businesses continue to grapple with the challenges of restrictions.

Two studies published on Tuesday in the prestigious journal Science concluded that the COVID-19 pandemic began in a market in the Chinese city of Wuhan, indicating a very likely animal origin of the virus, AFP reported.

The first study is a geographic analysis that shows that the first cases detected in December 2019 were concentrated around the market.

The second is a genomic analysis of the virus from the first cases, which shows it is unlikely that the virus was widely circulating in humans before November 2019. The debate has been raging since the beginning of the pandemic among experts who are trying to solve the mystery of the origin of the virus even now, almost three years later.