CBIC Epidemiology 3 — Questions and Answers
Question 1: A foodborne outbreak affects 40 of 100 people who ate potato salad and 10 of 100 who did not. What is the relative risk of illness from eating potato salad?
- 4.0 (Correct answer)
- 0.4
- 0.25
- 30
Correct answer: 4.0
Relative risk = attack rate in exposed (40/100 = 0.40) divided by attack rate in unexposed (10/100 = 0.10) = 4.0, indicating a fourfold higher risk in those who ate the potato salad.
Question 2: Which term describes the systematic, ongoing collection, analysis, and interpretation of health-related data essential to planning, implementing, and evaluating public health practice?
- Epidemiological investigation
- Public health surveillance (Correct answer)
- Outbreak response
- Contact tracing
Correct answer: Public health surveillance
Public health surveillance is the continuous, systematic process of collecting, analyzing, and interpreting data to guide timely public health action.
Question 3: In a prospective cohort study of SSI risk factors, the loss to follow-up of sicker patients would most likely introduce which type of bias?
- Recall bias
- Selection bias (Correct answer)
- Confounding
- Information bias
Correct answer: Selection bias
Loss to follow-up of sicker patients introduces selection bias because those who leave the study differ systematically from those who remain, distorting the true association between exposures and outcomes.
Question 4: Which generation time concept is critical when modeling person-to-person transmission of a respiratory pathogen in a hospital setting?
- Incubation period
- Serial interval (Correct answer)
- Infectious period
- Latent period
Correct answer: Serial interval
The serial interval—the time between symptom onset in a primary case and symptom onset in a secondary case—is critical for modeling transmission dynamics and predicting outbreak trajectories.
Question 5: A study reports an odds ratio of 0.3 for hand hygiene compliance and MRSA transmission. How should this be interpreted?
- Hand hygiene increases MRSA risk by 70%
- Hand hygiene reduces the odds of MRSA transmission by 70% (Correct answer)
- The association is not statistically significant
- Hand hygiene and MRSA transmission are unrelated
Correct answer: Hand hygiene reduces the odds of MRSA transmission by 70%
An odds ratio of 0.3 means the odds of MRSA transmission are 70% lower (1 - 0.3 = 0.7) among those with good hand hygiene compliance compared to those without.
Question 6: Which surveillance method involves reviewing a random sample of patient medical records to identify HAIs that may have been missed by other detection methods?
- Laboratory-based surveillance
- Physician-reporting surveillance
- Prevalence survey (Correct answer)
- Targeted surveillance
Correct answer: Prevalence survey
A prevalence survey (point prevalence or period prevalence) examines a cross-section of patients at a specific time to identify all active infections, often uncovering cases missed by routine surveillance.
Question 7: In infection control epidemiology, 'endemic' refers to which of the following?
- A sudden increase in disease occurrence above expected levels
- The constant presence of disease at a predictable rate in a defined area (Correct answer)
- A worldwide spread of disease across multiple continents
- An infection imported from another geographic region
Correct answer: The constant presence of disease at a predictable rate in a defined area
Endemic refers to the habitual presence of a disease or infectious agent within a given geographic area or population group at a predictable baseline rate.
CBIC Epidemiology 3
A foodborne outbreak affects 40 of 100 people who ate potato salad and 10 of 100 who did not.
What is the relative risk of illness from eating potato salad?