Pneumonia in small children commonly occurs in infants and toddlers under two years old, often starting abruptly. It usually begins with symptoms of an upper respiratory infection several days before onset. The main clinical symptoms are as follows: First, there is fever, which can be irregular, remittent, or persistent; in newborns or severely malnourished children, the body temperature may not rise or may be below normal. Second, there is coughing, which is generally frequent; initially, it is a dry, irritating cough, but during the peak of the illness, the cough may subside, returning with phlegm during the recovery period. Third, shortness of breath arises, typically after fever and coughing; sometimes it is accompanied by general symptoms such as listlessness, reduced appetite, restlessness, mild diarrhea, or vomiting.