200 people attended a party and some of them had diarrhea after 24 hours. They ate oyster, hamburger, ice cream, and potato salad. What’s the likely cause? 40 ill from 50 who consumed oyster 50 ill from 135 who consumed hamburger 60 ill from 140 who consumed salad 49 ill from 115 who consumed ice cream

**Core Concept**
The likely cause of the gastrointestinal illness is a foodborne pathogen, which is a microorganism that causes disease upon consumption of contaminated food. In this scenario, the pathogen is likely to be a bacterial or viral agent that is commonly associated with food poisoning.

**Why the Correct Answer is Right**
To determine the likely cause, we need to identify the food item that is most strongly associated with the illness. This can be done by calculating the attack rate (AR), which is the proportion of people who become ill after consuming a particular food item. The attack rate is calculated by dividing the number of people who become ill by the total number of people who consumed the food item. In this case, the attack rates for each food item are:

- Oyster: 40/50 = 0.8 (80%)
- Hamburger: 50/135 = 0.37 (37%)
- Salad: 60/140 = 0.43 (43%)
- Ice cream: 49/115 = 0.43 (43%)

The attack rate for oyster consumption is significantly higher than the other food items, indicating that oyster consumption is the most likely cause of the gastrointestinal illness.

**Why Each Wrong Option is Incorrect**
**Option A:** Hamburger consumption has a relatively low attack rate, making it an unlikely cause of the illness.
**Option B:** Salad consumption has an attack rate similar to ice cream, but the question stem suggests that oyster consumption is the most likely cause, making salad and ice cream less likely options.
**Option C:** Ice cream consumption has an attack rate similar to salad, but the question stem suggests that oyster consumption is the most likely cause, making ice cream and salad less likely options.

**Clinical Pearl / High-Yield Fact**
Vibrio vulnificus, a bacterium commonly found in raw oysters, is a leading cause of foodborne illness in the United States. It is particularly dangerous for individuals with underlying liver disease or compromised immune systems.

**Correct Answer: A. Oyster**

✓ Correct Answer: A. Vibrio parahaemolyticus