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.
A flat area of land between hills or mountains is called a valley. Valleys are usually formed by river water. The speed at which a river deepens its valley depends on the speed of the flow of the river water and the type of materials from which the river bed (the bottom of the river) is made.