Ready to boost your infection prevention prowess? Our Chain of Infection Quiz: Master the 6 Links & Stages challenges you to explore the chain of infection is a model of how germs travel - and test your grasp of each of the 6 links in the chain of infection. Dive into everything from reservoir to portal of exit, mode of transmission chain of infection to portal of entry chain of infection, and learn the essential steps of chain of infection for stopping outbreaks. If you enjoyed our communicable diseases reading and quiz or crave more hands-on practice with this infection control quiz , take this free challenge now and sharpen your skills!
What is the first link in the chain of infection?
Mode of transmission
Portal of exit
Causative agent
Reservoir
The first link in the chain of infection is the causative agent, which is the pathogen that can cause disease. Identifying the pathogen is crucial to understanding and interrupting the infection process. This link focuses on bacteria, viruses, fungi or parasites that invade the host. For more details, see CDC Chain of Infection.
Which of the following is considered a reservoir in the chain of infection?
Soil
Hands
Airborne droplet
Infected person
A reservoir is any habitat where the pathogen normally lives, grows, and multiplies. An infected person can serve as a biological reservoir because it harbors the pathogen and sheds it into the environment. Soil and hands can be transient carriers but are not the primary reservoirs in most human infections. Learn more at CDC Isolation Guidelines.
Which practice helps break the portal of exit for respiratory pathogens?
Using personal protective equipment (PPE)
Sterilizing surgical instruments
Administering broad-spectrum antibiotics
Covering the mouth when coughing or sneezing
The portal of exit is where pathogens leave the host. Covering the mouth when coughing or sneezing traps respiratory droplets and prevents them from dispersing into the environment. This interrupts disease spread by blocking the exit pathway. For more information, see CDC Isolation Precautions.
Which link in the chain of infection is defined as the route by which a pathogen is transferred to a susceptible host?
Susceptible host
Portal of exit
Portal of entry
Mode of transmission
Mode of transmission refers to how a pathogen is transferred from a reservoir to a new host, either directly or indirectly. It encompasses contact, droplet, airborne, vector-borne, and other routes. Interrupting transmission is critical to preventing new infections. Explore details at CDC Transmission Basics.
Which of the following is NOT a direct mode of transmission of pathogens?
Droplet spray from a sneeze or cough
Handshake
Airborne dust particles
Kissing
Direct transmission requires close physical contact or droplet spread between an infected source and a susceptible host. Airborne dust particles represent an indirect route because pathogens hitch a ride on dust and travel through the air without direct person-to-person contact. This makes it an indirect mode of transmission. See WHO Transmission Q&A.
Which barrier method is specifically aimed at interrupting the portal of entry?
Quarantining infected individuals
Disinfecting environmental surfaces
Wearing gloves when handling infectious materials
Vaccination
The portal of entry is how a pathogen enters a susceptible host. Wearing gloves creates a physical barrier that prevents pathogens from contacting broken skin or mucous membranes. This stops pathogens at their entry point. More on barrier methods at CDC HAI Prevention.
Immunization primarily protects which link in the chain of infection?
Portal of exit
Reservoir
Mode of transmission
Susceptible host
Immunization strengthens the host's immune defenses, reducing susceptibility to infection. It does not directly affect the pathogen's environment, transmission, or exit routes. By protecting the host, vaccines break the chain at the last link. Read more at CDC Immunization Basics.
Using sterile technique in surgery primarily breaks which link in the chain of infection?
Susceptible host
Portal of entry
Mode of transmission
Reservoir
Sterile technique ensures that surgical instruments and environments are free of pathogens. This prevents organisms from entering the patient's body during invasive procedures. Hence, it interrupts the portal of entry. For guidelines, visit CDC Sterile Processing.
Decontamination of hospital surfaces most directly interrupts which link in the chain of infection?
Causative agent
Reservoir
Mode of transmission
Susceptible host
Decontaminating surfaces removes or kills pathogens on inanimate objects, stopping indirect spread via fomites. This directly interrupts the mode of transmission by eliminating the vehicle that carries the pathogen. It does not change the host's susceptibility or the pathogen's characteristics. More at CDC Environmental Cleaning.
What is an example of a fomite in indirect transmission of pathogens?
Contaminated doorknob
Saliva
Respiratory droplets
Mosquito
A fomite is an inanimate object that can carry and transfer pathogens. A contaminated doorknob can harbor microorganisms and facilitate indirect transmission when touched by others. Mosquitoes are vectors, and droplets and saliva are direct forms of transmission. Learn more at CDC Environmental Transmission.
Which control measure specifically targets the reservoir link of the chain?
Vaccination
Quarantining infected individuals
Using gloves
Hand hygiene
Quarantine separates and restricts the movement of infected people, reducing opportunities for a pathogen to spread from its reservoir. This isolates the source, effectively targeting the reservoir link. Hand hygiene and gloves address transmission and entry, while vaccination protects the host. More at CDC Quarantine Guidelines.
Mosquito control programs primarily break which link in the chain of infection for malaria?
Portal of entry
Reservoir
Mode of transmission
Susceptible host
Mosquitoes act as vectors, carrying the malaria pathogen between people. Controlling mosquito populations interrupts this mode of transmission and stops the cycle of infection. It does not directly affect the pathogen or the host's immunity. For vector control strategies, see WHO Malaria Programme.
During a hospital outbreak of Clostridium difficile, which combined interventions would best interrupt multiple links in the chain of infection?
Use of UV air purifiers and mosquito nets
Administration of broad-spectrum antivirals and temperature screening
Rigorous hand hygiene and antibiotic stewardship
Mandatory vaccination of staff and sterilization of linens
Rigorous hand hygiene removes pathogens on hands, interrupting transmission, while antibiotic stewardship reduces disruption of normal flora, lowering the reservoir of C. difficile. This combination addresses both transmission and reservoir links effectively. Other options either target irrelevant vectors or do not impact C. difficile specifically. More info at CDC C. difficile Prevention.
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AI Study Notes
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Study Outcomes
Identify the 6 links in the chain of infection -
Recognize and name each of the 6 links in the chain of infection, from the infectious agent and reservoir to the portal of entry and susceptible host.
Describe the portal of entry chain of infection -
Explain how pathogens gain access to the host through various portals of entry and why this step is critical in disease development.
Analyze modes of transmission in the chain of infection -
Differentiate between direct and indirect mode of transmission chain of infection and assess how each contributes to the spread of pathogens.
Outline strategies to break the chain of infection -
Apply targeted interventions at each step of the chain to prevent transmission and reduce infection risk in clinical and community settings.
Evaluate risk factors for infection spread -
Assess host, environmental, and agent-related factors that influence infection transmission and develop prevention plans accordingly.
Test your knowledge with real-world scenarios -
Use our interactive quiz to reinforce your understanding of the steps of chain of infection and sharpen your clinical decision-making skills.
Cheat Sheet
Understanding the 6 Links in the Chain of Infection -
The chain of infection is a model of six interconnected steps - infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host - that explain how pathogens spread (CDC, 2023). Visualize the steps of chain of infection using the mnemonic "I-REMP-H" (Infectious agent, Reservoir, Exit, Mode, Portal, Host) to remember each link. Mastering this overview helps you pinpoint where to break the cycle.
Infectious Agent and Reservoir Dynamics -
Not all microbes are equally virulent; characteristics like ability to survive outside a host and infectious dose determine risk (WHO, 2022). Recognize common reservoirs - humans, animals, soil, water - and link them to specific pathogens (e.g., Legionella in water systems). A quick mnemonic is "HASP" (Human, Animal, Soil, Pool) to recall reservoir types.
Portal of Exit and Portal of Entry Chain of Infection -
Portals of exit (e.g., respiratory droplets, blood) allow pathogens to leave their reservoir, while portals of entry (e.g., mucous membranes, breaks in skin) let them invade a new host (Johns Hopkins Medicine, 2021). Matching exit and entry sites - such as droplet exit/inhalation entry - clarifies transmission risk. Remember "SEE" (Skin, Eyes, Ears) to list major entry points quickly.
Mode of Transmission Chain of Infection -
Pathogens can spread via direct contact, indirect contact (fomites), droplet, airborne, or vector-borne routes (mode of transmission chain of infection) according to epidemiological studies (NEJM, 2020). Use the acronym "DIDAV" (Direct, Indirect, Droplet, Airborne, Vector) to categorize modes swiftly. Understanding each mode guides targeted prevention measures like PPE or environmental controls.
Strategies to Break the Chain of Infection -
Interventions - such as hand hygiene at the portal of exit, disinfection of reservoirs, barrier methods at portals of entry, and immunization of susceptible hosts - interrupt transmission (NIH, 2021). Apply the "SAFE" approach: Sanitize, Apply barriers, Filter air, and Educate patients to cover all six links. Consistent use of these steps of chain of infection reduces nosocomial and community infections.
