CIC Outbreak Investigation 4 — Questions and Answers
Question 1: In a hospital outbreak investigation, which element is essential to include in a case definition during the initial phase?
- The suspected causative organism confirmed by culture
- Clinical criteria, time period, place, and person characteristics (Correct answer)
- The mode of transmission and source vehicle
- Laboratory-confirmed cases only to ensure specificity
Correct answer: Clinical criteria, time period, place, and person characteristics
An initial case definition includes clinical criteria, time (onset period), place (unit or facility), and person characteristics and may be sensitive rather than highly specific.
Question 2: Which scenario best represents a propagated epidemic curve pattern?
- All cases occurring within a 24-hour period at a single event
- Cases occurring in successive waves approximately one incubation period apart (Correct answer)
- Cases with a gradual rise and slow decline over several months
- A sharp peak followed by immediate cessation of new cases
Correct answer: Cases occurring in successive waves approximately one incubation period apart
Propagated outbreaks show successive waves of cases separated by intervals approximately equal to the incubation period, reflecting person-to-person transmission.
Question 3: An ICP is investigating a cluster of Pseudomonas aeruginosa infections in a burn unit. Which initial environmental sampling site should be prioritized?
- Ceiling tiles and air vents in the patient rooms
- Hydrotherapy equipment, sink drains, and water outlets (Correct answer)
- Surfaces of staff workstations and computer keyboards
- Bedside rails and IV pump surfaces
Correct answer: Hydrotherapy equipment, sink drains, and water outlets
P. aeruginosa is a waterborne organism that colonizes moist environments, making hydrotherapy equipment, sink drains, and water outlets the highest-priority sampling sites.
Question 4: The secondary attack rate in a household is best defined as:
- The proportion of susceptible household contacts who develop illness after exposure to a primary case (Correct answer)
- The overall proportion of all household members who become ill
- The rate of illness among community contacts of household members
- The number of new cases per 1,000 household members per day
Correct answer: The proportion of susceptible household contacts who develop illness after exposure to a primary case
The secondary attack rate measures the proportion of susceptible contacts in a defined setting who develop illness after exposure to a primary case, reflecting transmission efficiency.
Question 5: During an outbreak investigation, information collected in the line list reveals that all cases worked the night shift. This finding most directly suggests:
- The outbreak is due to a waterborne pathogen
- A time-place association that may indicate a common exposure on the night shift (Correct answer)
- The pathogen has a 12-hour incubation period
- Night-shift workers have lower vaccination rates
Correct answer: A time-place association that may indicate a common exposure on the night shift
A clustering of cases by work shift suggests a common exposure associated with the night shift environment, schedule, or shared equipment.
Question 6: Which agency in the United States has primary responsibility for investigating multistate foodborne disease outbreaks?
- State health departments in each affected state
- Centers for Disease Control and Prevention (CDC) (Correct answer)
- Food and Drug Administration (FDA) only
- United States Department of Agriculture (USDA)
Correct answer: Centers for Disease Control and Prevention (CDC)
The CDC coordinates multistate foodborne outbreak investigations, working with state health departments, FDA, and USDA depending on the implicated food product.
Question 7: After implementing control measures during a healthcare outbreak, which action is critical to determine if the intervention was effective?
- Performing environmental cultures weekly for one year
- Continuing active surveillance to monitor case counts and determine if the epidemic curve declines (Correct answer)
- Interviewing staff about compliance with the new protocol
- Sending all remaining environmental isolates for whole genome sequencing
Correct answer: Continuing active surveillance to monitor case counts and determine if the epidemic curve declines
Ongoing active surveillance after implementing control measures is essential to determine whether case counts decline, confirming intervention effectiveness.
CIC Outbreak Investigation 4
In a hospital outbreak investigation, which element is essential to include in a case definition during the initial phase?