Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi. The diseases can be spread, directly or indirectly, from one person to another.
Infectious pathologies are usually qualified as contagious diseases (also called communicable diseases) due to their potential for transmission from one person to another. Transmission of an infectious disease may occur through one or more diverse pathways including physical contact with infected individuals. These infecting agents may also be transmitted through liquids, food, body fluids, contaminated objects, and airborne inhalation.