What is the most common cause of pneumonia?

The most common cause of pneumonia is bacteria. This respiratory infection occurs when bacteria enter the lungs and cause inflammation, leading to symptoms such as cough, fever, and difficulty breathing. Streptococcus pneumoniae is one of the most frequently identified bacterial pathogens responsible for pneumonia, but other types of bacteria can also lead to this condition.

Bacterial pneumonia is especially prevalent in certain populations, such as young children, the elderly, and individuals with weakened immune systems or underlying health conditions. While viral infections and other factors can also lead to pneumonia, bacterial causes are predominant, making this the correct answer.

Other choices, such as drugs and excessive drinking, can contribute to weakened immune systems or increase susceptibility to respiratory infections but are not direct causes of pneumonia themselves. Similarly, going out in the cold with wet hair is a common myth and does not directly cause pneumonia. Understanding the primary role of bacteria in this illness helps clarify the importance of preventive measures, such as vaccination and maintaining a healthy immune system.