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.
There are three common types of valleys which include V-shaped valleys, U-shaped valleys, and flat-floored valleys. A V-shaped valley, sometimes called a river valley, is a narrow valley with steeply sloped sides that appear similar to the letter V from a cross-section. They are formed by strong streams, which over time have cut down into the rock through a process called downcutting.