New developments on the origins of Covid-19 have emerged after information pertaining to the illness of three researchers from the Wuhan Institute of Virology came to light. The researchers became so sick in November of 2019 that they sought hospital care, according to a previously undisclosed US intelligence report. The new information will likely add weight to growing calls for another probe into how the Covid-19 virus developed and whether it escaped from a laboratory. The disclosure of the researchers’ illness comes on the eve of a meeting at the World Health Organization at which the entity is expected to discuss the next phase of its investigation.

The researchers allegedly had symptoms consistent with both Covid-19 and common seasonal illness. The researchers were working on studies pertaining to coronaviruses and other pathogens, according to the State Department fact sheet. The information was issued during the final days of the Trump administration. The timing of the illness and hospital visits are cause for suspicion, according to experts, who state that the claims must be investigated. November 2019 is when many epidemiologists and virologists believe the SARS-CoV-2 strain began circulating around Wuhan, however, Beijing claims that the first confirmed case didn’t occur until December of 2019. The Wuhan Institute has not shared raw data, including safety logs and lab records on its extensive work with coronaviruses in bats at the lab.

Read More: Intelligence on Sick Staff at Wuhan Lab Fuels Debate on Covid-19 Origin