PITTSBURGH — UPMC is recommending, not requiring masks at its hospitals and outpatient facilities. That is a change in guidance the hospital system gave on Monday when officials said masks would be required to reduce transmission of respiratory viruses. In a statement, UPMC said “To protect the health and safety of our employees, patients and visitors, everyone in our health care facilities will wear effective masks, which reduce transmission of respiratory viruses in health care settings. We will continue to monitor the number of cases in our communities and adjust as the situation evolves,” But, now UPMC’s website states that masks are recommended in inpatient care facilities, like hospitals outpatient centers, urgent care and senior living facilities. The reason for the change in guidance was not immediately clear.