Chain of Infection

• Infectious Agent


  The microorganism (bacteria, virus, fungus, or parasite) that causes the disease.
• Reservoir


  The host or inanimate object in which the infectious agent normally lives and multiplies
• Portal of exit


  The way in which the infectious agent leaves the reservoir
• Mode of transmission


  The way in which the infectious agent is transferred from the reservoir to a susceptible host
• Portal of entry


  The way in which the infectious agent enters a susceptible host
• Susceptible host


  A person who is not immune to the infectious agent and can therefore become infected