virus
intracellular parasires that consist of DNA & RNA core surrounded by protein coat and sometimes a lipoprotein coat
bacteria
tiny, primitive cells that lack nuclei; cause infection by parasitism tissues or otherwise disrupting normal function
fungus
simple organisms similar to plants but lack chlorophyll pigments that allow plants to make their own food; they must parasite other tissues, including those of human body
protozoa
protists, one-celled organisms larger than bacteria whose DNA is organized into nucleus
prions
proteins that may cause misfolding of protein molecules, converting normal proteins of cell into different proteins
Rickettsia
any group of small bacteria that includes causative agents of typhus and various other febrile diseases in humans
pathogenic animal
large, multicellular organisms such as insects and worms; can parasite human tissues or disrupt normal body function
autoimmunity
immune system attacks one's own body
circadian rhythm
roughly 24 hour cycle in physiological processes of living beings