1. Substances, microorganisms or characteristics of individuals that may influence the progression of a disease or the likelihood of becoming ill. 2. A substance, such as a metallic ion or coenzyme, that must be associated with an
enzyme for the
enzyme to function. 3. A situation or activity that may increase a person's susceptibility to
AIDS. Examples of such cofactors are other infections, drugs and alcohol use, poor nutrition, genetic factors and stress.