Wuhan Institute of Virology researchers working on coronaviruses were hospitalised with symptoms consistent with COVID-19 in early November 2019 in what US officials suspect could have been the first cluster. The US is also examining whether the institute developed SARS-COV-2 while working on a coronavirus vaccine. The US State Department's former lead investigator into the origins of COVID-19, David Asher, said the possibility could not be ruled out that the vaccine was being developed as an "antidote" to a bioweapon.Mr Asher, who has served under both Republican and Democrat administrations, has previously led US government investigations into biological, chemical and nuclear proliferation in Iran and North Korea.He said US intelligence that has now been declassified, along with information from public sources, has crediblyconfirmed that three workers from the Wuhan Institute of Virology fell sick in early to mid-November 2019, prior tothe official start of the pandemic. Their illness was consistent with both COVID-19 and influenza and, in his personal assessment, was the likely cause of the outbreak.THEAUSTRALIAN.COM.AU12:05Wuhan Institute of Virology 'highly probably' the source of COVID-19 The former lead investigator who spearheaded a taskforce for the US government into the origins of COVID-19 hasdeclared the virus may have been the result of work done for a biological weapons program in Wuhan. "There were multiple staff members who did have to go to hospital and appeared to have had conditions ofCOVID-19," he said. "You don't normally go to the hospital with influenza, especially a cluster of people. This is the most probable source of the outbreak."It was possible, Mr Asher said, that there were clusters of COVID-19 prior to this outbreak in November, pointing toa spike in influenza in China in the autumn of 2019 that he said may have included coronavirus cases.A week ago, Mr Asher told Fox News that in his opinion, COVID-19 may have been a bioweapon. When asked by The Australian whether this was an active line of inquiry within the US government, he said: "Yes." "There is a high probability the Chinese government was engaged in a weaponisation effort at the Wuhan Institute ofVirology and other institutes involving coronavirus research," Mr Asher said. "Whether offence or defence, which isalmost impossible to tell, it was 100 per cent undeclared and that is a serious violation of the Biological WeaponsConvention and the WHO International Health Regs -- to the extent it spilled out and over somehow."Mr Asher said one theory on the table was that COVID-19 emerged during vaccine development, potentially even asan antidote to a bioweapon. "There's evidence certain scientists have found ... that there was adenovirus present inthe sequences posted publicly," Mr Asher said. The Wuhan Institute of Virology last month. Picture: AFP"Adenovirus means that there was a vaccine present for COVID-19; that could indicate that this was a bio-defenceproject putting a vaccine together. "People don't normally develop a vaccine for something they are working on. That doesn't make any sense ... todevelop a vaccine in advance for something that would never see the light of day makes it sort of ridiculous but istotally consistent with a biological weapons program. They develop an antidote."A WHO team member who visited Wuhan on the recent study tour, Marion Koopmans, had confirmed that "one ortwo" workers fell sick. Her view was that it was not unusual and she did not indicate any employees had beenhospitalised.The US State Department declassified intelligence in a statement dated January 15, 2021, where it was first revealed that Wuhan Institute of Virology workers had fallen sick in the autumn of 2019.At the time, the information was dismissed by critics, as secretary of state Mike Pompeo was hitting out at China onhis way out of office. Former deputy national security adviser for the Trump administration Matt Pottinger has since confirmed that USintelligence agencies had authorised the release of the information contained in that statement.Mr Asher's revelation that at least one Wuhan Institute of Virology employee required hospitalisation takes the information a step further. While some scientists and politicians say COVID-19 likely emerged naturally, Mr Asher said in his assessment itprobably came from a laboratory.