I spent 8 days in the Amazon on vacation. We flew into Iquito, Peru, got on a small fishing boat, and headed west. We got onto smaller rivers that fed into the Amazon and were led by an Indian guide.
It rained every day for short periods of time, and we were there during the flood season. We had smaller life boats that were tied to the larger boat. They were aluminum boats with 15hp gas motors, and we would anchor the main boat and take the smaller boat into the flooded forest. As long as you were on the water, the mosquitos were not bad, but start walking the forest and they were like all over you in a heart beat. The guide taught us to break off parts of the termite mounds and rub it on our exposed skin. Army termites guard the mound, and spit a fluid at the invading insects and it is a natural insect repellant. The mound is full of this dried spit. A little water, some dried spit makes a little mud, rub it right in.
The guides were armed with rifles, and they never went anywhere without being armed. At night, the big boat never stopped moving...fear of being attacked by local Indians. When the big boat stopped so we could get in the little boats it was always anchored in the middle of the river. We went into two villages. General population of about 75 people in each village. They own nothing but the skin on their backs and the knowledge of the jungle. And they were happy healthy people. The soil in the Amazon is bad because it is washed away by the flooding. They can plant some basic crops but the soil cannot support them for very long, so they just move to another area and start over again.
I could write for days about that place, but the Reader's Digest version is "eat or be eaten." Pretty rough neighborhood.