These are the main points we worked on ourselves and taken from the LZ Timeline:
People infected via bites or the initial flu are turned into '28 days later' rage-style runners, they are not killed by the infection. Only when they are killed in this
state to they reanimate and become traditional Romero style slow
zombies. With the flu-infection, the time from infection to full blown 'runner' can vary from hours to days. With bodily fluid transfer (ie bites) this can happen within minutes if the dose on infected fluid transfered is large enough.
Initial symptoms are fever most likely caused by the body's own immune system
All initial infected persons are runners. These people can be killed just like any non-infected person. When they die/are killed they reanimate as 'shamblers' in the traditional 'Romero' style. These can only be killed by destroying the brain.
The intial flu-type means of infection seems to have ended by the time the camps are over-run. there is the possibility that the flu still exists somewhere. After the camp system collapses then vast majority of infections are caused by transfer of bodily fluids (ie bites or infected fluid getting into open wounds)