In long range treks and expeditions as well as during any sort of survival situation it is important to keep infections and health problems at bay because under such peculiar circumstances they can be rather more troublesome than in the course of normal city life; fortunately, a rational use of fire could help a lot to keep a certain level of hygiene.
During such activities, especially if their duration is
considerable, the component of our kit will certainly be in contact with
the ground, dust, plants and so on. Indeed, places like public transit
areas within cities and towns are not exactly clean even if they look
like that, but while in the moddle of the wilderness it is unlikely that
you will find the same sort of dirt than in cities, you should assume
that the risk of infection does exist there as well, and there are many
cases to prove it. Nature is beautiful, but who said that it is clean?