Children are most commonly infected. Estimated prevalence rates among children in various world regions are 4â28%. Ascariasis: Ascaris, or roundworm, infection is the common helminthic infection in humans, with an estimated worldwide prevalence of 1 billion. The causative organism, A lumbricoides, is cosmopolitan in distribution, being most abundant in tropical countries.
Definition of hollow. 1  1 : an unfilled space : cavity, hole in the hollow of a tree. 2  2 : a depressed or low part of a surface; especially : a small valley or basin.
Streams usually form rivers in the higher elevations of mountains and hills. The areas of depression between hills or mountains are known as valleys. A river in the mountains or hills will usually have a deep and steep V-shaped valley as the fast moving water cuts away at the rock as it flows downhill.