As NBC News has reported, U.S. intelligence agencies first detected signs of a health crisis in Wuhan in November, and began producing intelligence reports on the issue in December.
The National Security Council began meeting about coronavirus in early January, according to NBC News reporting.
Secretary of State Mike Pompeo said on ABC Sunday that "there is enormous evidence … I can tell you that there is a significant amount of evidence that this came from that laboratory in Wuhan." But he declined to detail that evidence.
No one has credibly suggested the virus was engineered by humans. Pompeo said he accepted the scientific consensus that the virus was naturally occurring.
Two labs in Wuhan were studying coronaviruses. Researchers from both facilities collected the virus samples from bats in caves.
In the accidental release scenario, a worker at one of the labs could have become infected and transmitted the virus to others. Those who suspect such a lab release point to the following:
A Jan. 24 study published in the Lancet medical journal found that three of the first four cases — including the first known case — did not provide a documented link to the Wuhan wet market.
The bats that carry the family of coronaviruses linked to this new strain are not found within 100 miles of Wuhan — but they were studied in both labs.
Photos and videos have emerged of researchers at both labs collecting samples from bats without wearing protective gear, which experts say poses a risk of human infection
A U.S. State Department expert who visited WIV in 2018 wrote in a cable reported by the Washington Post: "During interactions with scientists at the WIV laboratory, (US diplomats) noted the new lab has a serious shortage of appropriately trained technicians and investigators needed to safely operate this high-containment laboratory."
According to intelligence committee member Sen. Tom Cotton, R.-Ark., the Chinese military posted its top epidemiologist to the WIV in January.
The Shanghai laboratory where researchers published the world's first genome sequence of the novel coronavirus was shut down Jan. 12, according to the South China Morning Post.
According to U.S. intelligence assessments, including one published by DHS and reviewed by NBC News, the Chinese government initially covered up the severity of the outbreak. Government officials threatened doctors who warned their colleagues about the virus, were not candid about human-to-human transmission and still have not provided virus samples to researchers.