Unusually for a Hollywood production, this film does not feature a musical score.

Both Jaume Balagueró and Paco Plaza -directors of the original movie [Rec] (2007)- have expressed their big dissatisfaction with this movie.

The apartment complex was a set but a fully functioning one with four floors.

Shot in chronological order.

In October 2008 Knott's Berry Farm theme park in Buena Park, California, had a Quarantine-themed walk-through "maze" for the park's 36th annual Knott's Scary Farm Halloween Haunt. It was their third movie-themed Halloween Haunt maze, after Beowulf (2007) and The Grudge 2 (2006).

The average shot was between 4 and 6 minutes long.

It took 4 hours for Doug Jones to get into his full-body prosthetic. His role required him to film for just one day.

Was not screened for US critics.

Remake of [Rec] (2007). [Rec] 2 (2009) was filmed in the same building, but Quarantine 2: Terminal (2011) wasn't filmed in the same building, but in a plane and in an abandoned building.

Both Jennifer Carpenter and Steve Harris have starred as comic book characters in the Batman saga. Carpenter would go on to voice Selina Kyle in Gotham by Gaslight (2018) and Harris voiced detective Ian Bennett/Clayface in The Batman (2004-2008)

(at around 41 mins) All rabies symptoms in the film are depicted accurately.

Jennifer Carpenter specifically asked that she never see the attic set. That way, she would know nothing about what to expect to see there, let alone be familiar with any of its geography.