What characterizes pneumonia?

Pneumonia is primarily characterized as an infection that inflames the air sacs in one or both lungs, which can be caused by various infectious agents. The correct answer identifies pneumonia specifically as a bacterial infection of the lungs.

In a bacterial pneumonia, bacteria overwhelm the lung’s defenses, leading to inflammation and filling of the alveoli with pus, fluid, and other cellular debris. Common bacteria that cause pneumonia include Streptococcus pneumoniae and Haemophilus influenzae. This type of infection typically presents with symptoms such as cough, fever, chest pain, and difficulty breathing.

While pneumonia can also be caused by viruses and fungi, the focus of the question is on the general characteristics that define pneumonia as an infectious disease, making the identification of bacterial infection as a key characteristic particularly relevant for understanding its nature and treatment. Other options, while related to respiratory conditions or infections, do not accurately describe pneumonia itself, as they refer to infections located in different parts of the respiratory system or involving different pathogens.