[quetzthecoatl]

they don't necessarily need to figure out the germ theory to know that diseases spread from proximity and/or contact with sick people when it happens right in front of them.

Also, there could be many such reasons for burying/burning someone dead with his/her possessions. My point was that almost always it becomes "elaborate rituals and beliefs of afterlife with same worldly possessions that they had here on earth" - just because we know pharaohs/ancient Egyptians did it.