A mobile Covid-19 testing lab in Wuhan, China, Aug. 5.

Photo: Wu Zhizun/Zuma Press

Independently in 1978, two groups in New York City and Germany came to the same conclusion: The previous year’s flu was so genetically similar to a variant last seen in the early 1950s that it could only have started from a stored lab specimen. The obvious candidates: China or Russia, in whose border regions the virus first manifested itself.

It was only in 2004, thanks to a Chinese virologist’s private word to a U.S. counterpart, that the world at large finally learned the release was likely the result of a vaccine trial in which Chinese military recruits were intentionally exposed to the 1950s virus.

“Virologists and public health officials with the appropriate sophistication were quickly aware that a laboratory release was the most likely origin,” wrote clinical pathologist Martin Furmanski in a 2014 examination of the incident, “but they were content not to publicize this, aware that such embarrassing allegations would likely end the then nascent cooperation of Russian and Chinese virologists.”

Suppressing such a finding today wouldn’t be easy, but the incentives are larger given the West’s economic relationship with China.

In assigning the intelligence community its 90-day mission to examine the lab-leak hypothesis, the results of which are due this month, Joe Biden may have been doing less than meets the eye, but he wasn’t doing nothing. Impetus is always needed to get the agencies looking into their vast trove of unexamined intercepts, laboriously figuring out whether a coded or whispered communication, when matched with other evidence, reveals more than intended.

Our intelligence community doesn’t like to say “we don’t know.” It likes to “estimate” probabilities. Unless they surprise themselves with a smoking gun that can’t be interpreted away, watch their body language. Do they emphasize the evidence or the uncertainty?

Here’s betting it will be the latter. Nothing gleaned by the intelligence snoops can put Covid back in its bottle. It’s hard to see any political upside for Democrats. Unless the Biden administration’s popularity is in free fall in three weeks and needs a foreign conflict to revive it, every incentive points toward changing the subject.

A study of the public record by House Republicans shows that reasons to suspect a lab leak are not in short supply: evidence that China moved to conceal records of the Wuhan lab before the outbreak became publicly known, doctored scientific data on the web, and distorted the history of a lab strain most closely related to the Wuhan virus.

Hospital parking-lot photos and Baidu search terms hint that Covid symptoms were rampant in Wuhan three months before Beijing acknowledged the virus’s existence. This evidence supports only the perception, strange enough, that Covid-19 sprang up out of nowhere in Wuhan. It doesn’t clarify whether it did so naturally or unnaturally. But a suggestive detail stressed in the House report is China’s failure to invest in the search for Covid’s origins after January 2020, as if it already knew the answer.

In the unlikely event the U.S. wanted to take the question further, how might it proceed? Recruit the right people, issue unambiguous marching orders and provide them a very large budget. One plausible avenue would be to scour the world for early Covid samples and the travel histories of their carriers. Thousands likely traveled through Wuhan during the period when Beijing seems to have suppressed news of the outbreak. If some sought care, if tissue samples are recoverable, a genetic family tree might shed light on the virus’s emergence. The scale of such a project would be daunting: finding the evidence, sequencing the fragments, analyzing their relationship. Going down this road does not lend itself to flexibility. If you invest humongously in finding the truth, you are then obliged to do something about it.

A little history: When Vladimir Putin rose to the presidency on the strength of his response to a terrorist bombing campaign that, by much credible evidence, was conducted by his own security forces, Western governments faced a choice. Acknowledge the evidence or look away to preserve Mr. Putin as somebody they could do business with, who might keep a lid on an unstable and potentially troublesome Russia.

In the case of the Wuhan lab-leak theory, wild cards might yet take a hand. Scientists and others will be poking around, trying to make sense of evidence in the public domain. Covid’s catastrophic nature, with the evolution of vaccine-resistent variants, is coming into sharper focus and a popular groundswell for accountability may arise. As Delta blows up in China itself, undermining its Covid smugness, Beijing’s power to intimidate is likely to wane. For the moment, the forecast of this column is that most of the world’s governments, not to mention the World Health Organization, are of one mind in preferring the mystery of Covid’s origins to remain a mystery.

As China's propaganda machine pushes to draw attention away from the Wuhan Institute of Virology, Americans who dismissed the lab-leak theory have a conflict of interest. Image: AFP/Getty Images Composite: Mark Kelly The Wall Street Journal Interactive Edition