Matheny and his wife quarantined after he apparently caught the virus from a family member. He has since recovered and is in camp with the Royals.
Kansas City named Matheny skipper last October. He took over for longtime Royals manager Ned Yost, who had announced his retirement during the 2019 season.
This will be Matheny's second stint as a major-league manager after serving as St. Louis Cardinals bench boss from 2012-18.