Where did covid-19 come from?
In the three years since the covid-19 pandemic began, one of the most persistent questions has been how the virus that caused it—SARS-CoV2—first jumped from animals to humans. SARS-CoV2 is one of a group of viruses, known as coronaviruses, commonly found in bats. But bats are rarely found in Wuhan, the Chinese city in which the virus emerged in December 2019. So how did humans come to be infected? Two theories have emerged: the “zoonotic” hypothesis, whose proponents argue that the virus jumped from animals to humans at a market in Wuhan; and the “lab leak” theory, according to which the virus escaped from a laboratory in the city. Which is right?