Infection can be caused by any of dozens of bacteria, viruses, and fungal organisms.
Inflammation can result from inhaling dust, chemicals, food, or vomit.
Pneumonia can be a very dangerous disease if it is not recognized and treated early. Oxygen then can't reach your blood. If your blood contains too little oxygen, your body's cells can't work properly and you become ill. There are several different kinds of pneumonia, but bacterial, viral, and a less typical type called mycoplasmal pneumonia are the most common. The viruses and bacteria that cause pneumonia are contagious and are usually found in fluid from the mouth or nose of an infected person.