PHILADELPHIA -- SEPTA said it is working closely with employees, unions and public health officials to monitor and address health issues associated with COVID-19 and the transit system.At least 11 SEPTA employees have tested positive for the virus.They work at various sites including the Comly Depot, the Norristown High-Speed Line Shop, Frankford Transportation Center, along the Market-Frankford Line, at the Allegheny Depot and the Elmwood Depot.SEPTA will continue notifying employees at the affected sites and provide updates online regarding employees who have tested positive.SEPTA reduced Regional Rail to an "Essential Service Schedule" as of Sunday.Here is a summary of the changes:Service on most lines will run every two hoursAirport Line service will run every hourTwelve of the 13 Regional Rail lines will operate seven days a week; Cynwyd Line service will operate Monday through FridayStarting Monday, SEPTA suspended overnight service on the Market-Frankford and Broad Street Lines between 1 a.m. and 4:30 a.m. to give crews additional time for cleaning amid the COVID-19 crisis.SEPTA said you can keep up with any additional changes on its website.