Nosocomial infections, also known as hospital-acquired infections, are diseases that occur more than 48 hours after a patient is admitted to the hospital. Infectious diseases that occur within 48 hours of admission are nosocomial infections, including infections that occur during hospitalization and infections that are acquired during hospitalization and develop clinical manifestations after discharge, when the patient is neither at the time of admission nor at the onset of the disease. The common causative organisms are predominantly Gram-negative bacteria, and the mode of transmission is mainly contact transmission. Some patients develop drug-resistant bacterial infections, such as methicillin-resistant Staphylococcus aureus and drug-resistant bacteria that are resistant to ultra-broad-spectrum drugs. Patients with nosocomial infections are usually sicker and can even be life-threatening. In addition, patients who are bedridden for a long time, repeatedly using antibiotics and immunosuppressed are at high risk for nosocomial infections, so care should be taken to avoid colds and flu, as well as timely discharge after the original disease is effectively controlled to avoid nosocomial infections. Therefore, patients need to be treated in isolation once nosocomial infection is diagnosed and treated with effective anti-infective therapy.