Construct An Epidemic Curve
Use infection evidence to construct an epidemic curve step by step.
- Transmission basics: Outbreak work depends on agent, host, route, time, and place.
- Case definition: Students need a rule for who counts as a case before counting cases.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Use infection evidence to construct an epidemic curve step by step.
Use the infection figure/table. Which evidence best supports a shared-source outbreak?
Reviewed- A.One person is much sicker than the others, with no exposure recorded
- B.Several cases share the same exposure and close onset times
- C.A large total case count, even when the exposures are all different
- D.Cases with onset dates spread evenly over six weeks
Show the worked solution ▾
Answer: B. Several cases share the same exposure and close onset times
- Step 1: Find shared exposure: A shared source means cases have a common exposure.
- Step 2: Check timing: Close onset times strengthen the pattern.
Why it's right: Shared exposure plus close timing supports a shared-source outbreak.
- A: How sick one person is does not show that other people shared a source.
- C: A big count with different exposures points to many sources, not one.
- D: Onsets spread evenly over weeks fit person-to-person spread, not one source.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
An epidemic curve is being drawn for a foodborne outbreak. What belongs on the horizontal axis, and what belongs on the vertical axis?
Reviewed- A.Number of cases along the bottom, and date of symptom onset up the side
- B.Date or time of symptom onset along the bottom, and number of cases up the side
- C.Patient identifiers along the bottom, and a severity score up the side
- D.Exposure location along the bottom, and date of symptom onset up the side
Show the worked solution ▾
Answer: B. Date or time of symptom onset along the bottom, and number of cases up the side
- Step 1: Ask what an epidemic curve shows: It shows how many people got sick and when.
- Step 2: Place the two quantities: When goes along the bottom and how many goes up the side, so the shape of the outbreak can be read left to right.
Why it's right: An epidemic curve plots time of onset along the bottom and case count up the side, so the rise and fall of the outbreak can be read across time.
- A: This flips the two axes, so the curve would no longer read across time.
- C: Individual identifiers are not a scale, and severity is not what an epidemic curve counts.
- D: Location is a different comparison; an epidemic curve is built on time.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
- In Unit 3.1 Outbreak Evidence, this skill turns class evidence into a result another person can check.
Fill these in as you work through the lesson.
- Pathogen (disease-causing agent):
- Transmission (how a pathogen spreads):
- Reservoir (where pathogen lives):
- Case (person who fits outbreak definition):
Track the , route of transmission, time pattern, and exposed before making an outbreak claim.
- Who fits the case definition?
- What exposure do cases share?
- What timing pattern appears?
Use the infection diagram or line list to practice construct an epidemic curve.