Chain of infection or transmission cycle represents the series of events taking place beginning with growth of the pathogen till the exit of the pathogen.
Explanation:
The chain of infection is parted with components like – starting with the infectious agent, the environmental reservoir, port of exit, transmission mode, port of entry, susceptible host.
The infectious agent - the actual disease-causing pathogen - microbes like bacteria, virus, fungi etc
The reservoir - the environmental area where the pathogen begins its life and lives like soil, water, animals, human, bio-equipment or biomaterial, etc
The port of exit - exit of the pathogen from its reservoir through open wounds, coughing, etc’
The mode of transmission of the pathogen - through direct or indirect contact or by inhalation or ingestion
Portal of entry refers to the entry of the pathogen to the host’s body through open skin, mucous membranes, respiratory tract, medical equipment like catheters, needles etc.
New susceptible host is the new host to which the pathogen enters. This is mostly a susceptible person who has been immunocompromised, weak with previous illness, receiving healthcare or with invasive medical or surgical equipment like lines, catheters etc