Pneumonias are infections that cause inflammation in the lungs, leading to symptoms such as cough, fever, and difficulty breathing. They can be caused by various pathogens, including bacteria, viruses, and fungi. The most common type is bacterial pneumonia, often caused by Streptococcus pneumoniae. Diagnosis typically involves a physical examination, chest X-rays, and sometimes laboratory tests. Treatment may include antibiotics for bacterial pneumonia or antiviral medications for viral cases. Vaccines are available to help prevent certain types of pneumonia, particularly in vulnerable populations like the elderly and those with weakened immune systems.