It's a shame about Mary

A recent study in Pediatrics finds Mary Ingalls of the LITTLE HOUSE ON THE PRAIRIE series likely did not lose her sight due to scarlet fever, as chronicled in BY THE SHORES OF SILVER LAKE, but rather had a viral brain infection. Next question: Was medicine just not far enough along to complete a differential diagnosis at the time, or did Wilder use scarlet fever as "a literary device," as claims a LITTLE HOUSE scholar?