The gameplay rundown video below does a great job of describing the concept, but basically Pandemic Express is Train to Busan Royale. 30 players meet up in a train station and one gets randomly infected. The goal of the game is for the one to try and infect the others before they can make it to the train out of the arena. There are guns and loot along the way, zombies get abilities and re-spawn instantly, and the final act takes place as the train pulls away and has to fight off the horde spawning on top of them.
Frankly I think it's an amazing concept and brings a whole new dimension to getting knocked out of a BR game as well as a whole new layer of cooperation in the dynamic of undead vs living struggle. You can wishlist the game now on Steam with a release price set to come in at around $10 with discounts at launch.
Fortnite to steal the idea and make Epic a bazillion dollars in 5... 4... 3... 2... 1...
