Streptococcus pneumoniae is the most common cause of community-acquired pneumonia. Pneumonia causes inflammation in the lungs and can range from mild to life-threatening. Risk factors include age, smoking, chronic illnesses. Typical pneumonia is often bacterial while atypical pneumonia can be caused by Mycoplasma, Legionella, or viruses. Symptoms depend on the pathogen but may include fever, cough, chest pain. Treatment involves antibiotics but severity assessment is needed to determine inpatient versus outpatient management. Prevention involves vaccination against influenza and Streptococcus pneumoniae.