Infectious Agent Transmission Flashcards

A healthcare worker develops chickenpox (varicella) after caring for a patient with disseminated herpes zoster. Which precaution failure MOST likely contributed to transmission?

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.

The basic reproduction number (R0) of a pathogen primarily reflects:

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.

Which type of host factor MOST increases susceptibility to infectious agent transmission?

Answer: Immunosuppression due to chemotherapy

Immunosuppression compromises the host's ability to mount immune defenses, dramatically increasing susceptibility to opportunistic and community-acquired infections.

Clostridium difficile spores are particularly challenging to eliminate because they:

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.

A long-term care facility reports multiple residents with influenza within 48 hours. The MOST likely transmission pattern is:

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.

Which environmental reservoir is most commonly associated with Legionella pneumophila transmission?

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.

Which precaution category is appropriate for a patient with measles (rubeola)?

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.