Source and agent CER

This is a MODEL from a different case, not the answer to today's reunion outbreak. Study how the pieces fit together, then build your own argument from your own curve, map, and test.\n\nScenario (parallel case): Campers at a lakeside summer camp fall ill with watery diarrhea over one week. Investigators have an epidemic curve, a spot map of cases by cabin, and a water sample result. They must name a likely source and agent.\n\nClaim: The likely source of the outbreak was untreated water from the camp's shallow well, and the likely agent was a waterborne protozoan parasite (Giardia).\n\nEvidence (three independent sources):\n- Epidemic curve: cases rose gradually and stayed elevated for about a week, a continuous-source pattern rather than one sharp peak.\n- Spot map: cases were spread across cabins on the well-fed side of camp, not clustered around any single meal or event.\n- Agent ID: a water sample from the well tested positive for Giardia cysts, a parasite spread through contaminated water.\n\nQuantitative measure: Attack rate = (24 cases / 80 campers using the well) x 100 = 30 percent.\n\nReasoning: A continuous-source curve means people kept getting exposed over days rather than all at once, which fits ongoing use of a water supply instead of one shared meal. The map locates the exposure with the campers who drank from the well, and the water test names the organism. Each tool answers a different question (when, where, what), and only together do they point to one explanation. A single peak would have suggested a one-time source, so the shape of the curve matters as much as the map and the test.\n\nAssumptions and limitations: I assume the count of 80 well users is accurate; if some listed campers actually drank bottled water, the true attack rate is higher. Onset dates were partly self-reported, so the curve's start could shift by a day. The positive sample shows the parasite was present in the water, but it does not prove every case drank from that well, so matching individual cases to well use would strengthen the claim.