What Is The Prognosis Of Acute Flaccid Myelitis?

A friend of my 16-year-old son has been diagnosed with acute flaccide myelitis. He was put in a medically induced coma a few weeks ago and has not woken up. He has been cleared as non-infectious. This is a new virus caused by enterovirus 68. His vitals are stabilizing and he was recently given a bronchoscopy. What is his prognosis?