Several U.S. states, including Oklahoma – where President Donald Trump is scheduled to hold a campaign rally – reported a surge in new coronavirus infections this week, ahead of what would be the nation's largest indoor social gathering since pandemic limitations were imposed.

The group of Donald Trump supporters camped out to see the president's first campaign rally in months has been growing larger and louder. The rally in Oklahoma is set to be the biggest indoor event in the country since pandemic restrictions were imposed in March.

Public health experts and some local officials are worried that thousands of people shouting and chanting inside an arena – particularly if many aren't wearing masks – could turn Trump's rally into a "super-spreader event" in a state that reported a record number of new cases this week.