GENEVA — All hypotheses on how the Covid-19 pandemic began remain open, the World Health Organization said yesterday, following an inconclusive four-year investigation that was hamstrung by crucial information being withheld.

The global catastrophe killed an estimated 20 million people, according to the WHO, while shredding economies, crippling health systems and turning people’s lives upside-down.

The first cases were detected in Wuhan in China in late 2019, and understanding where the SARS-CoV-2 virus that causes Covid came from is key to preventing future pandemics.

However, a lengthy investigation launched by the UN’s health agency said that pending further data, the origin of Covid and how it first spread remains elusive.

“As things stand, all hypotheses must remain on the table, including zoonotic spillover and lab leak,” WHO chief Tedros Adhanom Ghebreyesus told a press conference, referring to the two main hypotheses as to how the pandemic began.