A disease is a disorder that prevents the body
organs from working as they should. In general, diseases can be classified as
being infectious or noninfectious. Infectious diseases are caused by organisms
that invade the body and do harm to the cells, tissues, and organs. As a rule,
there is disease specificity when a specific disease-producing organism causes a
particular disease. Disease-producing organisms are said to be pathogens and are
described as being pathogenic. Noninfectious diseases are caused by factors
other than pathogenic organisms. Among the factors that are responsible for
noninfectious diseases are genetic causes, malnutrition, exposure to radiation,
emotional disturbances, organ failure, poisoning, endocrine malfunctioning, and
immunological disorders. Whatever the cause, a disease works counter to the well
being of the diseased organism.
