Complex sentence: Parents are often able to "identify the exact date and time that their children's symptoms had begun, and their descriptions of the onset as' ferocious',' overwhelming'or' severe enough that we took him to the ER'".
Split into simpler sentences: Parents are often able to "identify the exact date and time that their children's symptoms had begun". Parents describe the onset as "' ferocious',' overwhelming'or' severe enough that we took him to the ER'".