Treyarch has been doing a good job in adding content to Call of Duty: Black Ops 4 since its launch in October of last year. The Pandemic mode is out today but if you haven't searched for information regarding the new addition, you may have missed the teaser clip that the developer released recently.
The clip sees the player taking control of an undead being, having just risen from the dead, in the now-released Pandemic Mode for Call of Duty: Black Ops 4. The clip can be found here, on Treyarch's official Twitter account, and if you want to experience it for yourself, just go into your game and start playing.
Call of Duty: Black Ops 4 is available on PC, PlayStation 4 and Xbox One.