Pneumonia caused by non-infectious factors is not contagious; however, some infections (e.g. viruses or atypical pathogens) are contagious, as follows. 1. Non-infectious: Pneumonia can be caused by allergic reactions to medicines or radiation exposure, and such non-infectious causes of pneumonia are not infectious. 2. Infectious: (1) Bacterial infections such as Streptococcus pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, etc. are the most common causes of pneumonia; although these pathogens can be transmitted through droplets, respiratory secretions, etc., as long as one’s own immunity is relatively good, one will not be infected with pneumonia in general. (2) Pneumonia caused by viruses or atypical pathogens, such as pulmonary anthrax, pneumonic plague, atypical pneumonia, and highly pathogenic human avian influenza viral pneumonia, is highly contagious. If there are patients with pneumonia around you, you need to take good precautions to avoid close contact with respiratory tract infections.