A nosocomial infection* is an infection that patients acquire while under medical care in hospitals, care facilities, or even in outpatient practices. According to the Robert Koch Institute (RKI), a nosocomial infection occurs when the day of infection (the day with the first symptom) appears at the earliest on the third day following admission. However, the incubation period of the disease may not clearly disprove that the infection was acquired in hospital.
The risk for contracting nosocomial infections varies depending on the institution or specialty. It is related to the types of medical therapies and procedures performed, as well as to underlying diseases of the patients concerned (so-called risk areas). The highest infection rates can be observed in intensive care units. There, patients are at high risk of infection, resulting from the severity of their disease, along with the associated intensive – and often also invasive – treatment. The type of infection depends on the previous illness and the individual susceptibility of the patient. Urinary tract infections, wound infections, ventilator-associated pneumonia, and primary sepsis are particularly common.
Experts speak of a nosocomial outbreak in the sense of the Infection Protection Act when two or more patients experience nosocomial infections following an inpatient or an outpatient medical treatment in which an epidemic connection is probable or suspected. About 15% of nosocomial outbreaks were caused by bacterial pathogens and 85% by viral pathogens. Although nosocomial infections must be reported, many outbreaks remain undetected or unreported.
*Nosocomial infections are sometimes called healthcare- or hospital-associated infections (HAI).