A 47-year-old farmer presents with 3 weeks of fever, malaise, dry cough, progressive dyspnoea, and weight loss. He is tachypnoeic with SpO₂ 88% on air. Chest examination reveals widespread wheeze and bilateral coarse end-inspiratory crackles. Chest X-ray shows diffuse bilateral reticulonodular and ground-glass opacities. Bloods show neutrophilic leucocytosis. He is a non-smoker with no prior lung disease.