In investigating a food-borne illness outbreak following a community picnic, which food should be determined as the most likely cause based on the attack rate?

The most likely cause of the food-borne illness outbreak can be determined by comparing the attack rates of the different food items consumed. The attack rate is calculated by taking the number of people who became ill after consuming a specific food item and dividing it by the total number of people who ate that food item, then multiplying by 100 to get a percentage.

In this scenario, the ham sandwich has the highest attack rate at 72%. This indicates that a significant proportion of those who consumed the ham sandwich experienced illness. A higher attack rate suggests a stronger association between the food item and the illness, making it the most probable source of the outbreak.

The other food items have lower attack rates, which indicates that fewer people who ate them became ill. For example, the potato salad’s attack rate is 45%, the fruit salad’s is 55%, and the grilled chicken’s is 30%. Although these items also had individuals falling ill, the lower percentages mean they are less likely to be the primary source of the outbreak compared to the ham sandwich.

Thus, focusing on the attack rates further illustrates why the ham sandwich is the most likely cause of the illness as the data clearly highlights it as the food item with the highest associated risk of sickness among