At first, Soper thought the freshwater clams that had been served to the family were a likely source, but not everyone who developed typhoid had eaten them.

起初，索珀认为，这家人吃过的淡水蛤蜊可能是病毒来源，但并不是每个患了伤寒的家庭成员都吃过这些蛤蜊。