[[File:Pneumonia.jpg|thumb|350px|left|Pneumonia]]
Pneumonia is an infection that inflames the air sacs in one or both lungs. The air sacs may fill with fluid or pus, causing cough with phlegm or pus, fever, chills and difficulty breathing. A variety of organisms, including bacteria, viruses and fungi, can cause pneumonia. Pneumonia can range in seriousness from mild to life-threatening. It is most serious for infants and young children, people older than age 65, and people with underlying health problems or weakened immune systems.
==Pneumonia vs. Bronchitis==
Of the two conditions, pneumonia is the more serious. Acute bronchitis involves inflammation in the bronchial passages - the large tubes that carry air into the lungs. It's a common form of infection usually seen in the winter months and most commonly caused by a virus. It usually resolves without treatment in seven to ten days, although the cough can sometimes last much longer - sometimes several weeks or months before it completely resolves. Pneumonia, on the other hand, the more serious of the two conditions, involves infection of the deeper lung tissue that surrounds the bronchial tubes. Pneumonia is more dangerous infection because the infection can spread into the blood vessels in the lungs and set up a blood stream infection that can spread throughout the body. In some cases, it can be fatal, particularly in people who have immune problems or who are older.
== Symptoms ==
Symptoms of pneumonia include sudden chills, increasing fever (38.5 to 40.5 degree Celsius) and profuse sweating. Occurrence of chest pain may be noted and is aggravated by breathing and coughing and in severe cases tachypnea (rapid breathing) is noticeable, ranging from 25 to 45 breaths per minute coupled with a difficulty of breathing. Headache, myalgia (muscle pains), and upper respiratory tract symptoms such as nasal congestion and sore throat may be initialized too.