This feels like a lost episode of Doctor Who, one of those dark apocalyptic ones. Even the 9th Doctor's here, well, but here he's a bad guy.
The VHS-kinda quality of the movie gives it a perfect atmosphere. I can't get over the fact that the first scenes after Cilian Murphy wakes up and goes out is some of the best I've ever watched, with the silence and the total lack of humans everywhere.
It's basically a zombie movie. With the zombies being fast as hell like the ones from Train To Busan, but what they did with the movie, I loved it.