Complex sentence: The symptoms were so severe that David had to be taken out of the chamber for treatment; he died 15 days later on February 22,1984, of Burkitt's lymphoma at the age of 12.
Split into simpler sentences: The symptoms were so severe that he had to be taken out of the chamber for treatment. He died 15 days later on February 22,1984, of Burkitt's lymphoma at the age of 12.