Polio, or poliomyelitis, is a highly contagious viral infection that can lead to paralysis, breathing problems, or even death. The term poliomyelitis is from the Greek polios poliÃ³s meaning, grey myelos myelÃ³s referencing the, spinal-cord and itis. Meaning inflammation polio can be classified as either symptomatic. or asymptomatic
1 Prions are proteins that can force conformational changes in natural proteins and seem to cause disease (kuru, new variant Creutzfeldt-Jakob disease, and fatal familial insomnia).  A virus is an obligate intracellular pathogen (meaning that it must live within the cells of its host in order to reproduce).
2. parasitic fetus. accidental parasite one that parasitizes an organism other than the usual host. facultative parasite one that may be parasitic upon another organism but can exist independently. incidental parasite accidental parasite.malarial parasite Plasmodium. obligate parasite (obligatory parasite) one that is entirely dependent upon a host for its survival.arasite. a plant or animal that lives upon or within another living organism at whose expense it obtains some advantage. See also symbiosis. Among the many parasites in nature, some feed upon animal hosts, causing diseases ranging from the mildly annoying to the severe and often fatal.