Hospital-acquired infections are infections acquired in hospitals, including infections that occur during hospitalization and infections acquired in hospitals and occurring after discharge, but excluding infections that have begun before admission or are in the incubation period at the time of admission and develop in hospitals. The main cases of hospital-acquired infections are as follows: 1. Infections without a clear incubation period, infections that occur after 48 hours of admission are specified as hospital-acquired infections; infections with a clear incubation period, infections that occur after exceeding the average incubation period from the time of admission are hospital-acquired infections. 2. The infection is directly related to the last hospitalization. 3. 4. Infections acquired by newborns during and after delivery. 5. Potential infections activated by clinical measures, such as herpes virus and Mycobacterium tuberculosis infections. 6. Infections acquired by medical personnel during work.