Although organisms such as bacteria function as parasites, the usage of the term<unk> " is usually more restricted. The three main types of organisms causing these conditions are protozoa (causing protozoan infection), helminths (helminthiasis), and ectoparasites. Protozoa and helminths are usually endoparasites (usually living inside the body of the host), while ectoparasites usually live on the surface of the host. Protozoa are single-celled, microscopic organisms that belong to the kingdom Protista. Helminths on the other hand are macroscopic, multicellular organisms that belong to the kingdom Animalia. Protozoans obtain their required nutrients through pinocytosis and phagocytosis. Helminths of class Cestoidea and Trematoda absorb nutrients, whereas nematodes obtain needed nourishment through ingestion. Occasionally the definition of<unk> " is restricted to diseases due to endoparasites.
Parasitic disease
Infectious diseases 
Blood-borne disease
Tropical disease
Autoimmune/inflammatory syndrome induced by adjuvants
Skin and skin structure infection
Viral disease
Skin infection