You probably have some idea of what pneumonia is, but here’s something you may be less sure about: What causes pneumonia in the first place? And what can you do to keep from getting it? While some risk factors for getting pneumonia can’t be changed, like your age or whether you have an underlying chronic condition, others can be managed or modified. And knowing the most common direct causes of pneumonia can help you avoid them. Read on for the knowledge that can help you ward off this lung infection—or skillfully navigate it if you do get it.