CIC Infectious Agent Transmission 4 — Questions and Answers
Question 1: A healthcare worker develops chickenpox (varicella) after caring for a patient with disseminated herpes zoster. Which precaution failure MOST likely contributed to transmission?
- Failure to use contact precautions only
- Failure to use airborne and contact precautions for disseminated zoster (Correct answer)
- Failure to implement droplet precautions
- Failure to use protective environment precautions
Correct answer: Failure to use airborne and contact precautions for disseminated zoster
Disseminated herpes zoster requires both airborne and contact precautions, as VZV can be transmitted via airborne droplet nuclei in addition to direct contact.
Question 2: The basic reproduction number (R0) of a pathogen primarily reflects:
- The minimum infectious dose required to establish infection
- The average number of secondary cases generated by one case in a fully susceptible population (Correct answer)
- The proportion of exposed individuals who develop clinical disease
- The duration of the infectious period
Correct answer: The average number of secondary cases generated by one case in a fully susceptible population
R0 represents the average number of secondary infections caused by a single infectious case in a fully susceptible population, indicating a pathogen's transmissibility.
Question 3: Which type of host factor MOST increases susceptibility to infectious agent transmission?
- Advanced age alone
- Intact skin and mucosal barriers
- Immunosuppression due to chemotherapy (Correct answer)
- Vaccination against common pathogens
Correct answer: Immunosuppression due to chemotherapy
Immunosuppression compromises the host's ability to mount immune defenses, dramatically increasing susceptibility to opportunistic and community-acquired infections.
Question 4: Clostridium difficile spores are particularly challenging to eliminate because they:
- Are transmitted via airborne droplet nuclei
- Resist killing by alcohol-based hand sanitizers (Correct answer)
- Require arthropod vectors for transmission
- Survive only on animate surfaces
Correct answer: Resist killing by alcohol-based hand sanitizers
C. difficile spores are resistant to alcohol-based hand rubs and require soap-and-water handwashing and sporicidal disinfectants (e.g., bleach) for elimination.
Question 5: A long-term care facility reports multiple residents with influenza within 48 hours. The MOST likely transmission pattern is:
- Common source outbreak from a single contaminated meal
- Propagated epidemic spread via droplet and contact routes (Correct answer)
- Vector-borne transmission from staff to residents
- Airborne transmission requiring negative-pressure isolation
Correct answer: Propagated epidemic spread via droplet and contact routes
Rapid spread among multiple residents suggests propagated (person-to-person) transmission via respiratory droplets and contact, typical of influenza outbreaks in congregate settings.
Question 6: Which environmental reservoir is most commonly associated with Legionella pneumophila transmission?
- Contaminated soil from potted plants
- Aerosolized water from cooling towers and potable water systems (Correct answer)
- Fecal contamination of food surfaces
- Animal feces in healthcare environments
Correct answer: Aerosolized water from cooling towers and potable water systems
Legionella proliferates in warm water systems (cooling towers, hot water tanks, decorative fountains) and is transmitted via inhalation of contaminated aerosols.
Question 7: Which precaution category is appropriate for a patient with measles (rubeola)?
- Contact precautions only
- Droplet precautions only
- Airborne precautions (Correct answer)
- Standard precautions only
Correct answer: Airborne precautions
Measles is transmitted via airborne droplet nuclei that can remain infectious in the air for up to 2 hours after an infected person leaves the room, requiring airborne precautions.
CIC Infectious Agent Transmission 4
A healthcare worker develops chickenpox (varicella) after caring for a patient with disseminated herpes zoster.
Which precaution failure MOST likely contributed to transmission?