1… A bunch of teens survive some kind of disaster and go see if they can find survivors. A chilling scene I recall had them finding a dead person who had fungus/mold growing on him.
2.Took place sometime in the 1920s-50s and had a boy going on adventures with an older female relative. At one point they show up at his parent’s house with a muskox or yak named Muscatel.
The first I checked out from the YA section in the early '00s and the second I read at a relatives in the same time period.