They are unique since they lack a genome. All other known infectious agents contain genetic material. Bacteria are often surrounded by a strong protective cell wall and replicate through simple cell division. Fungi may cause infections of the mouth, throat, lungs, and skin.
Parasites thrive on their host, often causing longlasting chronic infections.
Viruses are small packages of genetic material that can only replicate inside a cell. Introduction Prions - novel infectious agents differing from all other known pathogenic agents Prions infect animals and humans From Dr Jekyll to Mr Hyde Different prions affect different regions of the brain Prion disease arise in three different ways These pages are based on material from the 1997 Physiology or Medicine Nobel Poster.