There were 13 different strains of the coronavirus in Wuhan, China in December 2019, World Health Organization scientist Peter Ben Embarek told CNN in an exclusive interview.

Why it matters: Data gathered during the WHO scientists' first trip to investigate the origins of COVID-19 could point to an outbreak that was more widespread than previously understood.

• Some virologists believe that multiple strains in Wuhan as early as December could suggest that the virus had previously spread undetected.
• Embarek, a lead investigator for WHO's mission to Wuhan, declined to draw conclusions on this in his CNN interview.

Of note: WHO scientists also say that it's "extremely unlikely" the virus came from a laboratory accident — debunking a conspiracy theory that had taken root among some Americans in late 2020.

What to watch: WHO scientists hope to return to Wuhan to continue investigations, Embarek said.

Go deeper: WHO's COVID probe in China raises more questions than it answers