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Identifying HAIs

Identifying Healthcare-associated Infections (HAI) in NHSN
Any infection reported to NHSN must meet the definition of an NHSN healthcareassociated infection (HAI), that is, a localized or systemic condition resulting from an
adverse reaction to the presence of an infectious agent(s) or its toxin(s). There must be
no evidence that the infection was present or incubating at the time of admission to the
care setting. Clinical evidence may be derived from direct observation of the infection
site or review of information in the patient chart or other clinical records.
For certain, but not all, infection sites, a physician’s or surgeon’s diagnosis of infection
derived from direct observation during a surgical operation, endoscopic examination, or
other diagnostic studies or from clinical judgment may be an acceptable criterion for an
NHSN infection, unless there is compelling evidence to the contrary.
NOTE: Physician’s diagnosis of pneumonia alone is not an acceptable criterion for
healthcare-associated pneumonia.
HAIs may be caused by infectious agents from endogenous or exogenous sources.
Endogenous sources are body sites, such as the skin, nose, mouth, GI tract, or vagina
that are normally inhabited by microorganisms.
Exogenous sources are those external to the patient, such as patient care personnel,
visitors, patient care equipment, medical devices, or the healthcare environment.
The following special considerations are important when identifying HAIs:
Infections occurring in infants that result from passage through the birth canal are
considered HAIs.
The following infections are not considered healthcare associated:
o Infections associated with complications or extensions of infections already
present on admission, unless a change in pathogen or symptoms strongly
suggests the acquisition of a new infection.
o Infections in infants that have been acquired transplacentally (e.g., herpes
simplex, toxoplasmosis, rubella, cytomegalovirus, or syphilis) and become
evident ≤ 48 hours after birth.
o Reactivation of a latent infection (e.g., herpes zoster [shingles], herpes
simplex, syphilis, or tuberculosis).
The following conditions are not infections:
o Colonization, which means the presence of microorganisms on skin, on
mucous membranes in open wounds, or in excretions or secretions but which
are not causing adverse clinical signs or symptoms.
o Inflammation that results from tissue response to injury or stimulation by
noninfectious agents, such as chemicals.

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Identifying HAIs

Before an HAI is reported to NHSN, the person performing surveillance must decide that
the clinical, laboratory, and other diagnostic information gathered concerning the patient
satisfy the criteria for a particular type of HAI. To assist surveillance personnel in making
these decisions consistently, each module in this manual contains a listing of specific
infection sites used in the module and the criteria for determining the presence of an
infection at each of those sites. The definitions used in this manual are the only criteria
that should be used when identifying and reporting NHSN events. While all participants
may not agree with all the criteria, it is important that NHSN participants consistently use
them for reporting infections, so that metrics between hospitals can be appropriately
compared. The complete set of infection definitions, including all specific sites used for
SSI organ/space infections can be found in Chapter 17.
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