Build A Line List
Use infection evidence to build a line list 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 build a line list step by step.
| Case | Symptom | Onset | Exposure |
|---|---|---|---|
| A | cramps | Tue 8 PM | cafeteria |
| B | cramps | Tue 9 PM | cafeteria |
| C | none | -- | no cafeteria |
Use the infection figure/table. Which evidence best supports a shared-source outbreak?
Reviewed| Case | Symptom | Onset | Exposure |
|---|---|---|---|
| A | cramps | Tue 8 PM | cafeteria |
| B | cramps | Tue 9 PM | cafeteria |
| C | none | -- | no cafeteria |
- A.Several cases share the same exposure and close onset times
- B.A large total case count, even when the exposures are all different
- C.Cases with onset dates spread evenly over six weeks
- D.One person is much sicker than the others, with no exposure recorded
Show the worked solution ▾
Answer: A. 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.
- B: A big count with different exposures points to many sources, not one.
- C: Onsets spread evenly over weeks fit person-to-person spread, not one source.
- D: How sick one person is does not show that other people shared a source.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
Of 40 people who ate at the cafeteria, 10 fell ill. Of 60 people who did not eat there, 3 fell ill. What is the attack rate in each group?
Reviewed- A.25% among those who ate there and 5% among those who did not
- B.25% among those who ate there and 20% among those who did not
- C.40% among those who ate there and 60% among those who did not
- D.10% among those who ate there and 3% among those who did not
Show the worked solution ▾
Answer: A. 25% among those who ate there and 5% among those who did not
- Step 1: Divide the exposed group: 10 ill out of 40 exposed is 10 divided by 40, which is 0.25.
- Step 2: Divide the unexposed group: 3 ill out of 60 unexposed is 3 divided by 60, which is 0.05.
- Step 3: Read as percentages: 0.25 is 25% and 0.05 is 5%.
Why it's right: An attack rate is the ill divided by the total in that group. 10 of 40 is 25% and 3 of 60 is 5%.
- B: 3 of 60 is 5%, not 20%.
- C: 40 and 60 are the group sizes, not the share of each group that fell ill.
- D: These are the raw counts of ill people, not shares of each group.
Aligned to Biotechnology Research and Experiments · reading level ~grade 10
- 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 build a line list.