SATURDAY, Nov. 8, 2003 (HealthDayNews) -- Although pneumonia can happen to anyone at any time, it often follows a cold or the flu and is particularly common in the fall and winter.
Some 50 percent of all pneumonia cases are caused by viruses. These infections, which tend to cluster in the fall and winter months, are marked in the beginning by a dry cough, headache, fever and muscle pain. Viral pneumonia can lead to bacterial pneumonia.
The latter type of pneumonia can also follow upper respiratory infections such as colds or the flu. Symptoms include shaking, chills, high fever, chest pain and a phlegm-producing cough.
The very young, very old and those with suppressed immune systems are at particular risk.
Even though there are treatments for the various types of pneumonia, the illness can be fatal. Your best bet is to avoid falling ill in the first place. Try these prevention tips from the Mayo Clinic:
More information
The American Lung Association has more details on pneumonia.