When the Philadelphia Phillies met the Miami Marlins on the field last July, a batch of Marlins players were infected with coronavirus, although they didn't know it. One case led to 19 other cases -- a superspreader event, the US CDC said Thursday. But with no fans in the stands and strict measures requiring the use of masks, social distancing and other measures, the two MLB teams managed to spend 11 hours on the field together over the course of five games without spreading the virus there, the CDC researchers said. Social distancing and mask use worked, they said, and team members were safer outdoors than inside.