Eleven days before The Nightmare, something scary happened:
Chester had a Magic type specific virus, which was dormant for a while. Then, July 9 (eleven days prior), it "attacked" him! Talinda, by coincidence, wasn't there, so Mike stayed with Chaz on the way to the Nightingale Society.
"Am I going to die!?" he repeatedly asked.
Chester was okay after, or so we thought.
October 30, 2017 (three months, twenty-one days later). It was 10:30pm Pacific Standard Time, and Anna Shinoda (along with poor Otis) teleport (because of a small teleportation device) into the Nightingale Society with Mike who was barely conscious. The Presence attacked him in a similar manner as the virus did.
Because the Presence is negative and strong, none of the nurses could help.
October 31. 3:23am. Anna and Mike are alone in a room. She knew why he didn't say anything. She held her husband's hand, also scared.
Finally, Mike asked quietly, "Am I going to die?"