elijah, Yes it is only on a contagious disease happening. In a SHTF many of the dead bodies will not be contagious if they do not have a virus like HIV or other virus, and it is for a 4 to 6 day time frame. But it will bring in wild animals which I think is a problem. Many in a SHTF will let go of the dogs and these dogs will turn into wild bad dogs. Then you have the rats which carry every disease around.
But you are right that many contagious diseases can’t live in a dead body, they need a live body to keep them self alive.
Also another thing to keep in mind is will there be an bio virus developed that can stay alive in a dead body for longer or become airborne too! We do not know if a country has develop this.