Infection Chain, Standard Precautions and Asepsis

The Chain of Infection and Healthcare-Associated Infections

Infection control in phlebotomy relies on understanding how microscopic pathogens move from source to host. The chain of infection describes this pathway through six continuous links: the infectious agent, the reservoir, the portal of exit, the mode of transmission, the portal of entry, and the susceptible host. An infectious agent is a disease-causing pathogen such as a bacterium, virus, fungus, or parasite. The reservoir is any person, animal, arthropod, plant, soil, or substance in which this infectious agent normally lives and multiplies. An infected patient can be a reservoir; blood in a contaminated container is infectious material and a potential source of exposure, but is not necessarily a reservoir in which the pathogen normally lives and multiplies.

To spread, the pathogen must leave the reservoir through a portal of exit, which is the specific route of departure. Common portals of exit include the respiratory tract, an open wound, or blood exposed by a needle puncture during collection. Once outside, the pathogen relies on a mode of transmission to travel to a new host. This mechanism can involve inanimate objects, called fomites, such as a contaminated collection tube or tourniquet passed between individuals. In other situations, a vector, which is a living organism, often an insect or tick, transmits the infectious agent to humans. The pathogen then encounters a portal of entry, which is the pathway it uses to gain access to a new body, such as exposed mucous membranes or puncture wounds created by needles.

The final link in the chain is the susceptible host, an individual who lacks effective resistance against that specific pathogenic agent. In healthcare facilities, patients often have reduced defenses, putting them at serious risk for acquiring a healthcare-associated infection. A healthcare-associated infection is an infection that a patient acquires while receiving healthcare that was not present or incubating when care began. Breaking any single link in this chain interrupts transmission entirely. Hand hygiene is considered the single most effective action a phlebotomist can take to break the chain of infection and safeguard both the patient and themselves.