Which symptom is characteristic of pneumonia?

Difficulty breathing is a hallmark symptom of pneumonia, a condition characterized by inflammation of the lungs, typically due to infection. When the alveoli (tiny air sacs in the lungs) become filled with fluid or pus, it hampers the exchange of oxygen and carbon dioxide, making breathing laborious and often causing shortness of breath. This symptom can be exacerbated by other manifestations of pneumonia, such as coughing and fever.

In contrast, weight loss is not a direct symptom of pneumonia but can occur over time due to prolonged illness. Excessive energy levels would be atypical in the context of pneumonia, where fatigue and weakness are more commonly experienced due to the body fighting the infection. Frequent headaches can occur with various health conditions, including infections, but they are not specific to pneumonia and are often secondary to fever and inflammation rather than a primary symptom. Thus, difficulty breathing stands out as the most characteristic and concerning symptom of pneumonia.