An infectious disease is a clinically evident disease resulting from the presence of pathogenic microbial agents, including pathogenic viruses, pathogenic bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions. These pathogens are able to cause disease in
animals and/or plants. Infectious pathologies are usually qualified as contagious diseases (also called communicable diseases) due to their potential of transmission from one person or species to another. Transmission of an infectious disease may occur through one or more of diverse pathways
including physical contact with infected individuals. These infecting agents may also be transmitted through liquids, food, body fluids, contaminated objects, airborne inhalation, or through vector-borne spread.
Infectious Agents not covered here - CDC - Diseases and Conditions