BRUSSELS — As the coronavirus spread last year, former President Donald Trump and leading U.S. conservatives floated the idea that the virus may have escaped from a Chinese lab or was created by China as a bioweapon. China pushed back. A nine-month AP investigation, conducted in collaboration with the Atlantic Council's Digital Forensic Research Lab, found China launched what may be its first global digital disinformation campaign, using its growing presence on Western social media to seed and spread stories suggesting the U.S. created COVID-19 as a bioweapon.

Here are 6 key takeaways from AP's investigation:

1. Since 2016, Russia has been widely seen as the leading foreign actor spreading disinformation. With COVID-19, China took the lead, continuing to spread conspiracies about the origins of the virus long after Moscow stopped.

2. China has landed with a bang on Western social media. The number of Chinese diplomatic accounts on Twitter has more than tripled since mid-2019, while on Facebook they've more than doubled. Both platforms are banned in China. With COVID-19, these accounts helped set and amplify messaging across platforms, languages and geographies.

3. A series of 11 tweets by Chinese foreign ministry spokesman Zhao Lijian in March, which broadcast speculation that the U.S. Army engineered COVID-19, was cited over 99,000 times, in at least 54 languages, by accounts with hundreds of millions of followers. Then Chinese state media picked up and syndicated his ideas.

4. China leaned on Russian disinformation strategy and infrastructure. Conspiracies were seeded and spread through established Kremlin proxies in the West. China, Russia and Iran also reinforced each other's messaging, cross-referencing reports and sources, deepening their echo chamber of authenticity.

5. During the first half of 2020, there were millions of coronavirus-related interactions on Twitter with 829 accounts linked to the Chinese, Russian and Iranian governments. Chinese state media and Foreign Ministry accounts were among the most retweeted.

6. China's foreign ministry says it resolutely rejects disinformation, but will defend itself against the aggression of hostile forces seeking to politicize the epidemic. "All parties should firmly say 'no' to the dissemination of disinformation," the ministry said in a statement to AP, but added, "In the face of trumped-up charges, it is justified and proper to bust lies and clarify rumors by setting out the facts."