Sheila Knighton is a carrier of the Dorsavirus and the patient zero of a 2012 outbreak.
As of 2007, Sheila was being beaten by her husband and so stayed at a women's shelter for protection. At the time she'd been carrying the Dorsavirus, and in turn accidentally spread it to and killed the rest of the occupants of the shelter.
In 2012, Sheila met her father-in-law, Carl, and gave the Dorsavirus to him, it ultimately killing him. She also gave it to her husband's friend, Brad, who began to show signs even as soon as she'd left. She then went after her abusive husband, Jerry. As she was about to kiss him, The Arrow intervened and injured Jerry before he could hit her. He convinced Sheila to go to the Centers for Disease Control and Prevention (CDC) and turn herself in.