The new rule is the latest in a wave of stricter policies that tech companies are rolling out to confront an outbreak of virus-related misinformation on their sites.
Facebook and Google, which owns YouTube, have already put similar systems in place. Twitter rolled out a fact-check feature on tweets regarding mail-in voting ballots from President Donald Trump Tuesday, drawing the president's ire and eliciting a two-tweet tirade against the social media giant by Trump.
On Tuesday, Twitter added a warning phrase to two Trump tweets that called mail-in ballots “fraudulent” and predicted that “mail boxes will be robbed,” among other things.