Pneumonia, an infection of the lungs, can be caused by (1) the pneumococcus or certain other bacteria or (2) virases. Both types are infectious and can spread from person to person. Most people carry the pneumococcus and other pneumonia-causing germs in their throats at all times, but when they are well and strong, the germs do no harm. When the body is weakened, resistance to the pneumonia germs is lowered, and the body cannot successfully fight against them. The time to be most on guard is just after an ordinary cold begins, especially the third and fourth day, and during and after an attack of influenza, whooping cough, or measles. Overexposure to cold after a great deal of sweating, and insufficient rest, also create conditions favorable for an attack of pneumonia.
If the disease affects one or more lobes of the lung, it is called lobar pneumonia. When both lungs are affected, the lay person usually calls it "double pneumonia." The doctor terms it bilateral. Bronchopneumonia refers to pneumonía that is localized chiefly in or around the bronchial tubes. It is usually, but not necessarily, milder than lobar pneumonia.
