How did the transmission of SARS-CoV-2 to humans occur? Probably no scientific question is currently as politically charged as this one. Three years after the outbreak in Wuhan, there are still no clear answers, but many opinionated statements from supporters of a natural origin as well as a laboratory leak.

Last Sunday, the Wall Street Journal wrote that, according to a secret report, the US Department of Energy no longer – like two other American agencies – considers both theories to be similarly likely, but rather assumes a laboratory leak, albeit with "low certainty".

As early as 2021, media reported that the FBI assumed a laboratory origin – FBI chief Christopher Wray confirmed this on Fox News, but without citing any evidence. Other American authorities, on the other hand, adhere to the theory of natural origin. Two years ago, a study by the World Health Organization (WHO) and China described the laboratory thesis as "very unlikely", Beijing denies it anyway. After criticism, WHO chief Tedros later said that all hypotheses were on the table.

When the magazine "Nature" recently reported that the WHO had stopped a second phase of investigation, it again denied it; a panel of experts, to which Christian Drosten belongs, remains on the topic. The question is "very, very important," Tedros affirmed in mid-February – both in terms of science and to prevent future pandemic and in terms of morale: It is about knowing why millions of people have lost their lives.

It is doubtful whether such morally charged statements will help persuade Beijing to be transparent. He had asked a top official there a few weeks ago for cooperation, Tedros explained. Whether there was an answer, the WHO left open on request. It would probably help most if American intelligence services would present clear evidence. If they actually exist.