Wall Street Journal reported on Sunday, citing a US intelligence report.The newspaper said the previously undisclosed report — which provides fresh details on the number of researchers affected, the timing of their illnesses, and their hospital visits — may add weight to calls for a broader investigation into whether the Covid-19 virus could have escaped from the laboratory.The Journal said current and former officials familiar with the intelligence expressed a range of views about the strength of the report's supporting evidence, with one unnamed person saying it needed "further investigation and additional corroboration."The first cases of what would eventually be known as COVID-19 were reported at the end of December 2019 in the central.