Wuhan: thirty percent
Thirty percent. That was the probability Kristian Andersen privately assigned to a laboratory origin of COVID-19, according to Slack messages released in July 2026. Andersen co-authored the March 2020 Nature Medicine paper that dismissed laboratory scenarios as implausible. Thirty percent leaves quite a lot of room for “we don’t know.”
Then there was the separate Lancet letter, which condemned origin-related “conspiracy theories” and declared no competing interests. Signatory Peter Daszak ran EcoHealth Alliance, which funded coronavirus research at the Wuhan Institute of Virology. The fuller disclosure came in 2021.
The emails behind that letter are more entertaining than the letter. “No need for you to sign the ‘Statement’ Ralph!!” was the subject of Daszak’s email to Ralph Baric. Keeping their names off would distance the statement from their collaboration. Baric agreed: “Otherwise it looks self-serving and we lose impact.” Daszak ultimately signed; Baric did not.
The honest message would have been simple: we don’t know where it came from, and here is our funding relationship. Readers could have handled both facts.
There is also a distinction that keeps getting lost: a lab leak does not require an engineered virus. A naturally occurring virus collected from a bat remains naturally occurring in a laboratory freezer. Evidence against engineering does not tell us how it reached its first human host. For that, laboratory records matter alongside evidence from animals and early cases.
WHO’s investigators ran into that problem. In 2025, its advisory group said the available evidence favoured an animal origin, while WHO reported that China had not supplied requested laboratory and biosafety information. An investigation is difficult when the filing cabinet stays shut.
Chornobyl: six missing pages
Chornobyl had its own international authority: the IAEA, whose remit includes both promoting peaceful nuclear energy and establishing safety standards. An awkward pair of jobs when nuclear energy has just blown a roof off. As with the Lancet and WHO, the question is how independently an institution can scrutinise the people whose expertise and cooperation it needs.
At the August 1986 meeting in Vienna, Valery Legasov presented the Soviet account. According to nuclear engineer Alexander Sich’s account of physicist Richard Wilson’s findings, about six pages on radioactive releases over Belarus had been removed on Legasov’s instructions. You could make the report cleaner without making Belarus any cleaner.
Sich also recounts Legasov’s later admission: “I did not lie at Vienna, but I did not tell the whole truth.” Legasov died by suicide on 27 April 1988, the day after the disaster’s second anniversary.
But some evidence had escaped the editors. On 28 April 1986, radiation alarms at Forsmark in Sweden alerted investigators to fallout from abroad. The Soviet authorities could remove pages from a report. They could not remove radioactive material from someone else’s detector.
The cost of not knowing
COVID-19 had outside investigators too. In 2023, the FBI publicly said it considered a laboratory-associated incident the likely origin. The FBI’s assessment did not settle the dispute. A virus crosses borders without saying where it started.
We studied COVID-19 as a virus and fought it as an epidemic. But what happened in Wuhan? Chornobyl invites questions about reactor design, operators and oversight. Wuhan still invites an argument about a laboratory and a market. Millions died, yet we cannot reconstruct the chain of events that started it.
That makes openness more necessary. We can improve wildlife-trade safeguards and laboratory safety while the origin remains unresolved. Records could reveal failures—or help clear an institution wrongly suspected of them.
Thirty percent and six missing pages are different stories with the same lesson: institutions earn trust by making their claims checkable. Tell us what you know, tell us whom you fund, and let someone else open the filing cabinet.