What is a major symptom of Legionnaire's disease?

Legionnaire's disease primarily presents with symptoms of pneumonia, which is a significant and defining characteristic of this infection. The pneumonia caused by Legionella bacteria can manifest clinically with a dry cough, typically not accompanied by the thick, purulent sputum often seen in other types of pneumonia caused by different pathogens. This dry cough is a result of the lung tissue being affected and inflamed, leading to difficulty in producing mucus as the body responds to the infection.

The other symptoms associated with Legionnaire's disease can include fever, chills, and shortness of breath, but the hallmark feature remains the pneumonia, which can vary in presentation. Also, unlike many other respiratory infections where a productive cough is common, the cough associated with Legionnaire's disease tends to be dry, indicative of the disease's specific pathophysiological effects. Therefore, the correct choice is the one that highlights the key symptom of pneumonia with a dry cough, aligning with the clinical presentation of Legionnaire's disease.