Betsy McKay, Amy Dockser Marcus, Natasha Khan and Jeremy Page :

Tiny vials of bat saliva in a laboratory in Wuhan, China, collected with help from U.S. government funding, potentially hold clues to the origin of Covid-19 or the next pandemic.

They are now mostly out of reach of U.S. scientists, part of a bitter international controversy that has effectively stalled a high-stakes hunt for the source of the coronavirus that causes Covid-19 and also made the world less prepared for future health crises.

One fallout from the conflict over the origin of the pandemic is less scientific collaboration and more mistrust between two global powers that must work together with other nations to head off or mitigate the next disaster.

“We are very vulnerable,” said Dr. Jeremy Farrar, director of Wellcome, a London-based charitable foundation that funds health-related research. “I don’t think there is nearly as much cooperation and partnership going on as there was in December 2019.”

The breakdown stems from the early days of the pandemic when U.S.-China relations—already strained over trade and security—plunged to new lows as a lack of transparency from China was exacerbated by finger-pointing from the U.S.