. >> pelley: robyn and britta garfield are among the 40 patients enrolled in the university of pennsylvaniatherine werner, robyn garfield is a trade officer with the commerce department. he was posted with his wife and two young children in shanghai. >> robyn garfield: i don't know when the sound started. i do know that it was for months on end. >> britta garfield: i was sitting next to robyn, and something, i felt like, hit me from the left side. and at first it felt like an electric shock, and then it paralyzed me, so i was not able to move or speak. >> pelley: it hit you so hard you felt like you were in danger in the room? >> britta garfield: yes. >> pelley: they say the children suffered blurred vision and loss of balance. your daughter was literally falling down? >> robyn garfield: yes. she fell down multiple times that day. >> britta garfield: we went on a walk and she just fell on her face. it was very abnormal. she never does that. and then a second time, she completely lost her balance and just fell to the side. >> pelley: in 2018, then- secretary of state mike pompeo confirmed th