Thousands in China, Southeast Asia infected annually by animals carrying coronaviruses, raising pandemic risk: study

An average of 400,000 such infections occur each year, most going unrecognised because they cause mild or no symptoms and are not easily transmitted between people, researchers with the EcoHealth Alliance and Singapore’s Duke-NUS Medical School said in a study released before peer review and publication. Still, each spillover represents an opportunity for viral adaptation that could lead to a Covid-like outbreak.

The question of where and how the virus that causes Covid-19 emerged has become particularly contentious, with some leaders blaming a hypothetical leak from a lab in Wuhan, China that studies the pathogens. The new research, supported by the US National Institute of Allergy and Infectious Diseases, builds on evidence that bats are the main host animals for viruses like Sars-CoV-2 and that people living near their roosts are especially vulnerable.

“This is probably the first attempt to estimate how often people are infected with Sars-related coronaviruses from bats,” said Edward Holmes, an evolutionary biologist at the University of Sydney who was not involved in the research.

Humans are continually exposed to bat coronaviruses, he said. “Given the right set of circumstances, one of these could eventually lead to a disease outbreak.”

Almost two dozen bat species that can be infected by coronaviruses dwell in an area of Asia more than six times the size of Texas, with southern China and parts of Myanmar, Laos, Vietnam and Indonesia deemed the riskiest for spillovers.