One of the main challenges (for WHO team) emerged after the experts learnt that more than 90 people needed hospital treatment for Covid-like symptoms in central China in the two months before the first official cases were recorded in Wuhan in December 2019.

It is widely believed that the virus must have been circulating before those known infections. But evidence of the earlier spread would embarrass Beijing.

China: coronavirus handling a stunning success & insisted no evidence the outbreak began on Chinese soil. Instead, it has pursued an Anywhere But China strategy, claiming it was imported in frozen food, originated in Europe or was engineered in a US military laboratory.

WHO team asked to test old waste water samples for traces of the virus. Analysis of sewage for diseases is a routine check, but were told the material had been “discarded”. Requested access to blood donations collected at the time, another standard check, again turned down.

China may run the world’s most sweeping surveillance state but the authorities said they had been unable to obtain permission to test samples held in blood banks. The request by the WHO team remains in place.

In epidemiological studies, we would normally be given results for each patient for line-by-line investigation. But here we were just given the aggregate data rather than having the opportunity to conduct our own analysis.

“We were not set up to conduct a forensic investigation of the (Wuhan) lab as that would be a matter for specific experts. So, yes, we had to rely on their answers and their data. Of course, you never know if anything is being withheld. That applies to all our work in Wuhan.”