REC Movies: Quarantine Films
The Quarantine films represent American adaptations that reimagine the REC concept for English-speaking audiences. While the first film closely follows the structure and plot of the original REC, it exists as a separate continuity with different characters.
Quarantine 2: Terminal shifts the outbreak to an airport setting and is an original sequel specific to the American version. These films can be enjoyed independently without knowledge of the Spanish versions, offering their own take on the infection outbreak concept.
There are 4 other watch orders available - see the links up above.

Quarantine
A television reporter and her cameraman become trapped inside a building under CDC quarantine when a mysterious virus outbreak turns residents into violent killers.

Quarantine 2: Terminal
When a mysterious virus takes over a passenger plane, the aircraft is placed under strict quarantine upon landing, forcing a group of survivors to work together to escape the deadly outbreak.
Other Film Series
Benson-Moorhead Universe
An interconnected indie sci-fi/horror universe from filmmaking duo Justin Benson and Aaron Moorhead.
Chernobyl
Feature films exploring the 1986 Chernobyl nuclear disaster and its lasting impact on the exclusion zone.
Cults
Films exploring the manipulation, devotion, and darkness of religious and psychological cults.
H.P. Lovecraft
Feature film adaptations directly based on the works of horror author H.P. Lovecraft.
Invasion of the Body Snatchers
Four films exploring alien pod people replacing humans, each updating the concept for different eras and anxieties.
Silent Hill
Horror films based on the acclaimed video game franchise, exploring the nightmarish town of Silent Hill through interconnected and standalone stories.