A senior Chinese epidemiologist said the United States should be the priority in the next phase of investigations into the origin of Covid-19 after a study showed the disease could have been circulating there as early as December 2019, state media said on June 17.

A report on the origins of Covid-19 by a U.S. government national laboratory concluded that the hypothesis of a virus leak from a Chinese lab in Wuhan is plausible and deserves further investigation, the Wall Street Journal said on June 7, citing people familiar with the classified document.

Top U.S. infectious disease expert Dr. Anthony Fauci called on China to release the medical records of nine people whose ailments might provide vital clues into whether Covid-19 first emerged as the result of a lab leak, the Financial Times reported on June 3.

President Joe Biden ordered aides to find answers to the origin of the virus that causes Covid-19, saying on May 26 that U.S. intelligence agencies are pursuing rival theories potentially including the possibility of a laboratory accident in China.

The United States called on May 25 for international experts to be allowed to evaluate the source of the coronavirus and the “early days of the outbreak” in a second phase of an investigation into the origins of the coronavirus.

A previously undisclosed intelligence report by the U.S. State Department shows that three scientists at China’s Wuhan Institute of Virology received hospital care in November 2019 for influenza-like symptoms. The findings were on a State Department fact sheet that said they went to the hospital “with symptoms consistent with both Covid-19 and common seasonal illness.”

The origin of the novel coronavirus is still unclear and the theory that it was caused by a laboratory leak needs to be taken seriously until there is a rigorous data-led investigation that proves it wrong, a group of leading scientists said.

A new global system should be set up to respond faster to disease outbreaks, which could ensure that no future virus causes a pandemic as devastating as Covid-19, an independent World Health Organization review panel said on May 12.

A new study by researchers at the University College London (UCL) published in Lancet Infectious Diseases finds that although the U.K. variant of SARS-CoV-2 known as B.1.1.7 is more transmissible than the wild-type, original Wuhan strain, it is likely not more deadly.

A joint China-World Health Organization (WHO) study into Covid-19 provided no credible answers about how the pandemic began, and more rigorous investigations are required – with or without Beijing’s involvement, a group of international scientists and researchers said on April 7.