The evidence derives from Florida and France and suggests the virus had already escaped Wuhan, China and begun travelling around the world at least as early as December.
Researchers tested samples from patients with respiratory illnesses who went to hospitals in December, January, and February.
Maria Van Kerkhove, the World Health Organization’s COVID-19 technical lead, said, “It’s really important that we look further into this. Some countries may look backwards and may look at some of those samples that were stored in January or in December and may retest those. It’s possible that we may see some of those samples testing positive for COVID-19.”