We Just Finished Supper And Were Talking Here At The

We just finished supper and were talking here at the table and my wife was suddenly hit with violent shivering. It reminded me of the shivering that one gets when coming down off of a malarial fever. She's not running a fever, however, and we've covered her up with blankets and placed a source of heat next to her back. She just can't get warm. Any thoughts?