For nearly two years, we followed three families as they grapple with this horrifying reality. Heres abcs chief medical correspondent, dr. Jen ashton. Here you go. Reporter this is the hill familys last hope. One for their 8yearold son quinton. Getting ready for a potentially lifechanging surgery. After a Mysterious Illness changed his life forever and left him partially paralyzed overnight. He was unable to move his neck, his arm or he had a really hard time walking. It was pretty scary. You feelin all right . Yeah. Reporter this moment may not just define quintons future. Can you give me a mask please. Reporter but the futures of children like him across the country, looking for answers. Here we go, buddy, hold my hand. Reporter and hope. A medical mystery. The scariest part of this is how little we know about it. Reporter as the country struggles to contain the covid19 epidemic, medical experts are sounding the alarm that another outbreak is hiding in the shadows. 2020 is expected t