Contamination
Contamination:
The presence of an infectious agent on a body surface, also on or in clothes, beddings, toys, surgical instruments or dressings, or other inanimate articles or substances including water, milk and food.
Infestation:
For persons or animals the lodgment, development and reproduction of arthropods on the surface of the body or in the clothing, e.g. lice, itch mite.
Infectious Diseases:
A clinically manifest disease of man or animals resulting from an infection.
Contagious Disease:
A disease that is transmitted through contact. Examples include scabies, trachoma, STD and leprosy.

Communicable Diseases:
An illness due to a specific infectious agent or its toxic products capable of being directly or indirectly transmitted from man to man, animal to animal or from the environment through air, dust, soil, water, food etc.
Epidemic:
The unusual occurrence in a community or region of disease, specific health–related behavior clearly in excess of “Expected occurrence”. It applies to infectious diseases as well as the “Slow modern epidemics” such as heart disease cancer etc.
Endemic:
It refers the constant presence of a disease or infectious agent within a given geographic area or population group, without importation from outside. For e.g. in some areas malaria has a constant presence called endemic malaria.
Zoonosis:
An infection or infectious disease transmissible under natural conditions from vertebrate animals to man e.g. rabies, plague, bovine tuberculosis.
Nosocomial infection:
Nosocomial (hospital acquired) infection is an infection originating in a patient while in a hospital or other health care facility. It includes infections acquired in the hospital but appearing after discharge, and also such infections which affects the working staff.
Opportunistic infection:
This is infection by a organism(s) that takes the opportunity provided by a defect in host defense to infect the host and hence cause disease. It is commonly seen in people whose immunity is compromised such as people who are on steroids.

Latrogenic Disease:
Any untoward or adverse consequence of a preventive, diagnostic or therapeutic regimen or procedure, that causes impairment, handicap, disability or death resulting from a physician’s professional activity or from the professional activity of other health professionals.