Outbreaks

An outbreak happens when a city that already has 3 cubes of a colour would receive a 4th: instead, the Outbreaks marker advances 1 space and every city connected to it gets 1 cube of that colour. If that pushes a connected city to its own 4th cube, it chains into another outbreak — moving the marker again and spreading again. If the Outbreaks marker ever reaches the last space of its track (8 outbreaks), your team loses immediately.