Final answer:
The subject of this question is Medicine. The symptoms described are indicative of a severe complication of influenza called necrotizing pneumonia.
Step-by-step explanation:
The subject of this question is Medicine. The symptoms described, such as young patient with recent influenza developing pneumonia with high fever, productive cough with hemoptysis, leukopenia, and multi lobar cavitary infiltrates, are indicative of a severe complication of influenza called necrotizing pneumonia. This occurs when the influenza virus damages the lung tissue and leads to the development of cavities filled with necrotic tissue and fluid.