What EXACTLY is the infection in Left 4 Dead?

No one actually explains what the infection or "Green Flu" is and what it does. Here's my first in-depth analysis video. I don't feel like I covered nearly enough on this topic, so let me know what else you would like to know! BIG THANKS to the Left 4 Dead Wikia: http://left4dead.wikia.com/wiki/Green... T-SHIRTS AND MERCH AVAILABLE HERE: http://rdbl.co/2ybCQ39 ___Social Media!___ Facebook: http://bit.ly/2ybo5xi Twitch:   / w0wsuchgaming   Twitter:   / wow_such_gaming   PATREON: http://bit.ly/2wo2GfI ___Friends Channels!___ Cake Slayer: http://bit.ly/2wnzohu DJ Timevoid: http://bit.ly/2xPaCKv Nanogerm:    / godnickl   Beejie Bean: http://bit.ly/2xQcymk Wow Such Gaming streams: http://bit.ly/2yc1XCV ___Music Talents!___ Background music by Ghost Memories (Ryan Torres):   / ghost_memories   ========================= Coaching Theme track- Run on by Zack Haygood:   / zack.haygood.9w