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What is pneumonia?
Pneumonia is an infection of the lungs, the lower part of the respiratory tract.
Different germs, like viruses, bacteria, fungi, or parasites, may cause pneumonia.
These germs commonly infect the nose and throat, causing colds and other upper respiratory tract infections. Pneumonia sometimes follows an upper respiratory infection (URI), if the germs get through the body's defenses and travel down the respiratory system into the lungs.
Viruses are the most common cause of upper respiratory infections in children and also, the most common cause of pneumonia.
The viruses that commonly cause pneumonia are adenovirus, rhinovirus, influenza virus (flu), and respiratory syncytial virus (RSV).
Children under 2 years of age are especially vulnerable to pneumonia caused by the RSV virus, especially during the winter. The bacteria that most often cause pneumonia are streptococcus pneumoniae and mycoplasma.
Pneumonia can be a complication of pertussis, also known as whooping cough. Pertussis is increasingly found in teenagers and adults, but is especially dangerous in very young infants.
The time from infection until symptoms appear (incubation period) for pneumonia depends on the type of germ causing the infection.
The germs that cause pneumonia are easily passed from one person to another, primarily through coughing, sneezing, or contact with body fluids.



