● The film is the first film in the history of Korean films with "The Flu Virus" as its theme.
● The film is Kim Sung-soo director Kim Sung-soo's comeback after 10 years of "English Complete Conquest Manual".
● The original plan for the film was to have Jo In Sung and Jang Hyuk co-starring, but Jo In became the work "Power Law" directed by Park Kwang Hyun, the righteous brother, and could not match the schedule with the producer, so the film finally finalized Jang Hyuk starring.
● The film is Su Ae's first female lead in a disaster film.
● Su Ae has been hesitant when receiving the invitation, because Director Kim is a director known in the film industry as "horrible, disgusting, fierce", which made Su Ae very scared, and later met the director and studied it carefully It was decided after the script was written.
● The film is Park Min-ha's debut.
● Before the filming, Jang Hyuk visited the fire station frequently to receive rescue knowledge courses from professional firefighters.
● During the filming, because Su Ae was a medical staff member, she often had to wear a mask. She felt that this "equipment" was too difficult to use, mainly because it was difficult to speak clearly in a chaotic environment.
● As an unmarried actress, it is difficult for Su Ae to show her mother's love in the play. The mother's love day in the play is what Su Ae figured out after recalling the stories about her growing up with her parents.
● The film was originally scheduled to be distributed by CJ E&M, but because the release time of CJ's "Snowpiercer" and "The Flu" was less than two weeks apart, in order to better announce "The Flu", CJ no longer acted as the film Distribution company, and changed to I Love Cinema's independent distribution. The decision to change the distribution company was made two weeks before the film's release, which is also very rare in the Korean film industry.
