Both Bernie Sanders and Joe Biden’s presidential campaigns canceled rallies scheduled for Cleveland on Tuesday night because of coronavirus concerns. This would be the first official disruptions the pandemic has caused in the Democratic primary.

In other announcements, the Democratic contenders’ campaigns said that they had exercised caution about holding large public gatherings after hearing guidance from public health officials. Both the Sanders and Biden campaigns thanked supporters who had intended to attend the events on an important day in the race to decide who faces President Donald Trump in November. 

In a statement, Sanders communications director Mike Casca said the Vermont senator’s campaign would evaluate whether future events will take place “on a case by case basis.”

Biden’s communications director Kate Bedingfield stated that the campaign would “make announcements about future events in the coming days.” The Democratic front-runner delivered remarks in Philadelphia at the National Constitution Centre at 9:30 p.m. ET. 

Questions have been posed about when the outbreak would affect a closely scrutinized and enormously consequential Democratic primary. Large gatherings where the virus could spread make up an essential part of Sanders’ strategy. Biden doesn’t rely on rallies as much as his rival. 

Washington state, one of the areas in the U.S. most affected by the outbreak, held its primary on Tuesday. While voters cast ballots by mail and did not physically go to the polls and risk spreading coronavirus, the state instructed voters not to lick the envelopes.