Carolyn Kormann writes in the New Yorker that for thousands of years, a parasite with no name lived happily among horseshoe bats in southern China. The bats had evolved to the point that they did not notice; they went about their nightly flights unbothered. One day, the parasite—an ancestor of the coronavirus, sars-CoV-2—had an opportunity to expand its realm. Perhaps it was a pangolin, the scaly anteater, an endangered species that is a victim of incessant wildlife trafficking and sold, often secretly, in live-animal markets throughout Southeast Asia and China. Or not. The genetic pathway remains unclear. But to survive in a new species, whatever it was, the virus had to mutate dramatically. It might even have taken a segment of a different coronavirus strain that already inhabited its new host, and morphed into a hybrid—a better, stronger version of itself, a pathogenic Everyman capable of thriving in diverse species. More recently, the coronavirus found a new species: ours. Perhaps a weary traveler rubbed his eyes, or scratched his nose, or was anxiously, unconsciously, biting his fingernails. One tiny, invisible blob of virus. One human face. And here we are, battling a global pandemic.
The world’s confirmed cases (those with a positive lab test for covid-19, the disease caused by sars-CoV-2) doubled in seven days, from nearly two hundred and thirteen thousand, on March 19th, to four hundred and sixty-seven thousand, on March 26th. Nearly twenty-one thousand people have died. The United States now has more confirmed cases than any country on earth, with more than eighty thousand on March 26th. These numbers are a fraction of the real, unknown total in this country and around the world, and the numbers will keep going up. Scientists behind a new study, published earlier this month in the journal Science, have found that for every confirmed case there are likely five to ten more people in the community with an undetected infection. This will likely remain the case. “The testing is not near adequate,” one of the study’s authors, Jeffrey Shaman, an environmental-health sciences professor at Columbia University, said. Comments from emergency-room doctors have been circulating on social media like S.O.S. flares. One, from Daniele Macchini, a doctor in Bergamo, north of Milan, described the situation as a “tsunami that has overwhelmed us.”
Scientists first discovered that coronaviruses originate among bats following the outbreak of Severe Acute Respiratory Syndrome (sars) in 2003. Jonathan Epstein, an epidemiologist at the EcoHealth Alliance in New York who studies zoonotic viruses—those that can jump from animals to people—was part of a research team that went hunting for the source in China’s Guangdong Province, where simultaneous sars outbreaks had occurred, suggesting multiple spillovers from animals to people. At first, health officials believed palm civets, a mongoose-like species commonly eaten in parts of China, were responsible, as they were widely sold at markets connected to the sars outbreak, and tested positive for the virus. But civets bred elsewhere in Guangdong had no antibodies for the virus, indicating that the market animals were only an intermediary, highly infectious host. Epstein and others suspected that bats, which are ubiquitous in the area’s rural, agricultural hills, and were, at the time, also sold from cages at Guangdong’s wet markets, might be the coronavirus’s natural reservoir.