American researchers suspect that a new COVID-19 variant, HKU5-CoV-2 virus, discovered in China, could lead to another pandemic. "HKU5 viruses may be only...small step away from being able to spill over into humans," said Michael Letko, a virologist who co-led the study. It's currently only spreading in bats, but experts fear China's unregulated wildlife trade raises risk of spillover events.