A breakthrough came from a 12-month-long survey at the cave in Yunnan. By collecting fecal samples from the horseshoe bats year-round, the scientists increased their chances of finding bats with active coronavirus infections. They found a SARS-like virus in a bat that in subsequent lab tests did have the ability to infect human cells. In a 2013 paper, they called it “the clearest evidence yet” that SARS not only originated in bats, but could directly infect humans without having to first go through an intermediate animal such as civets. “The eureka moment is a slow process,” said Dr. Wang. “You put the pieces together like a jigsaw puzzle.” For Dr. Wang, the critical piece of the puzzle came in a 2017 paper, over a decade after his trip to China on the WHO mission. Additional years of collecting bat samples from the same cave led to the discovery of a bat SARS-like virus even more closely related to the SARS outbreak one. They were finally ready to lay out the argument that the epidemic virus originated after a series of recombination events, when bats harboring various SARS-like viruses infected each other, with the viruses swapping genetic material to ultimately create the pandemic strain. They also issued a warning that other SARS-like coronaviruses capable of infecting people were already circulating among bats in the region. The emergence of another SARS-like epidemic was a very real possibility, they wrote.