As scientists find more animal coronaviruses, they can recognize more and more pieces of SARS-CoV-2 spread out among them. Researchers have also been able to reconstruct some of the evolutionary steps by which SARS-CoV-2 evolved into a potential human pathogen while it was still infecting animals.
This pattern is probably one that’s been followed by many viruses that are now major burdens on human health. H.I.V., for example, most likely had its origin in the early 1900s, when hunters in West Africa got infected with viruses that infected chimpanzees and other primates.
But some scientists thought it was too soon to conclude something similar happened in the case of SARS-CoV-2. After all, the coronavirus first came to light in the city of Wuhan, home to the Wuhan Institute of Virology, where researchers study dozens of strains of coronaviruses collected in caves in southern China.
Still, that a top lab studying this family of viruses happens to be located in the same city where the epidemic emerged could very well be a coincidence. Wuhan is an urban center larger than New York City, with a steady flow of visitors from other parts of China. It also has many large markets dealing in wildlife brought from across China and beyond. When wild animals are kept in close quarters, viruses have an opportunity to jump from species to species, sometimes resulting in dangerous recombinations that can lead to new diseases.
That lab’s research began after another coronavirus led to the SARS epidemic in 2002. Researchers soon found relatives of that virus, called SARS-CoV, in bats, as well as civet cats, which are sold in Chinese markets. The discovery opened the eyes of scientists to all the animal coronaviruses with the potential of spilling over the species line and starting a new pandemic.
Virologists can take many measures to reduce the risk of getting infected with the viruses they study. But over the years, some accidents have happened. Researchers have gotten sick, and they’ve infected others with their experimental viruses.
In 2004, for example, a researcher at the National Institute of Virology in Beijing got infected with the coronavirus that causes SARS. She passed it on to others, including her mother, who died from the infection.