it was a virus. you play as a member of a secret unit of trained undercover operators designed to retore the gov't should it fail because the gov't makes emergency planning scenarios for every possible or impossible contingency. really, just go look it up on youtube(the long interview with the game devs that also shows off the previous E3's tech demo/game reveal), you get the whole backstory there. basically the flu mutated and infected the currency and people went to shit in NYC. also f**k off, Tom Clancy is dead and mostly acted as a stand-in for a ghostwriter with the post rainbow 6(original series) games.