elijah, 1974 is right a pandemic will have the contagious diseases go every were in water.
But one of the biggest problems is the decaying bodies will contaminate the water supplies in your underground well water. HIV virus will be a live for up to six days after, and there maybe other viruses that do the same. After that there is no more contagious diseases alive but you will get a lot of animals which will bring a lot of diseases(rats). If there is a new epidemic(new Virus) that we do not know much about then all studies go out the door.
But after five to six days the bodies will not be contagious, but it will bring in a lot of wild animals which many have diseases so if anyone in your group gets bitten by one of these wild animals and there is no hospitals open then they may die too!