One of the key reasons why pandemic flu kills you is the cytokine storm–essentially a hyper-effective response of the immune system. The cytokine storm, in response to the invading flu virus, essentially leads to massive organ failure. Here’s a recent article from PNAS about strategies to control the flu-induced cytokine storm. The notion is that if we could do so, pandemic flu would, like seasonal flu, just be a miserable experience–not a life threatening one.
And here’s another article from PLoS showing just how complex this system really is. Recent attempts to dial down the cytokine storm using biologicals have been problematic.