Investigating Outbreaks in Health Care Settings: Step 4

Step four: Assess and evaluate encounters

Look for encounters and additional related cases during the exposure period to help determine if other people are at risk. To do this:

1. Create a chronological list of all health care encounters during the likely exposure period of the index case.
2. List procedures performed during each encounter, especially those involving percutaneous exposures or that are invasive (e.g., injections, infusions, skin puncture with a needle/lancet). Include HCP(s) involved in care, equipment used, medications administered, and room(s) where procedure(s) was performed.
3. Review the investigation database to see if there is a pattern of exposure with this facility/provider and enter the facility/provider(s) into the health care database.
4. Contact the facility to inform them of the investigation and determine if they are aware of the current case(s) under investigation or any additional infections.
5. Evaluate the health care facility by doing the following:
   1. Conduct a site visit
   2. Develop a list of potentially exposed patients
   3. Identify additional cases

Conduct a site visit

The purpose of the site visit is to gather information about the facility using the infection prevention and control checklist as your guide. You will interview staff and observe the same procedures as those performed on the index patient, ideally by the same HCP(s). If the facility is not performing the same procedures during the visit, consider having HCP(s) perform mock procedures so you can observe typical practices.

Medication and equipment

Pay attention to medications or equipment used for more than one patient and any opportunities for diversion of theft of controlled substances. This should include handling and preparation practices of drugs like opioids, psychotropic drugs, and performance-enhancing drugs (e.g., epoetin, darbepoetin) the facilities may stock.

Facility staff as the source

You should assess the potential for facility staff to be the source of infection (e.g., through diversion of narcotics, sexual abuse of residents).

Facility differences

Evaluate each facility based on its unique features and practices, focusing on procedures involving percutaneous exposures, injections, and intravenous medications. For example:

• In a long-term facility, pay attention to assisted blood glucose monitoring and periodic visitors like dentists, podiatrists, or wound care specialists.

• In a hospital, assess admissions and the patient's room, but also observe all areas of the hospital where the patient received care or had procedures done like the operating room, radiology, or the emergency department.

• In all types of facilities, consider the behavior and practices of individual residents including potential sexual activity.

If a complete investigation is not possible, then you should, at a minimum, send a follow-up letter to potentially impacted health care facilities as a reminder to review their infection prevention practices, and continue to monitor surveillance data for several months to ensure no additional cases are identified.

Develop a list of potentially exposed patients

This list should contain all people who were seen on the same day or at the same time as the index patient. You can then develop a chronologic listing of patients who may represent additional cases or sources of infection for the index patient.

The appropriate time period before and after the index patient visit is typically 1–2 days, but this will depend on a number of factors including the:

• Index case's number of facility visits

• Patient volume of the facility

• Types of procedures being performed

• Infection prevention practices observed during the visit

For example, if the facility was a hospital, the list might only include patients from the relevant unit or patients who overlapped in the same operating room.

Identify additional cases

Identify additional cases by cross-matching your list with acute and chronic disease registries and lab reports. Cross-matching may not result in additional findings. Recent studies estimate that about 50% of chronic hepatitis C cases and an estimated 68% of chronic hepatitis B cases nationwide remain undiagnosed. Given this high proportion of undiagnosed infections, targeting testing can be more beneficial.

If multiple encounters have been identified, you should prioritize your investigation based on the following:

• Information obtained from the investigation database and regulatory complaints.

• Types of procedures the facility performed on the index patient (prioritize those involving percutaneous exposures, e.g., injections, infusions, skin puncture with a needle/lancet).

• Timing of these procedures in relation to the likely exposure period for those infected.

• Settings and procedures where outbreaks have been reported.

If a complete investigation is not possible, then you should, at a minimum, send a follow-up letter to potentially impacted health care facilities as a reminder to review their infection prevention practices, and continue to monitor surveillance data for several months to ensure no additional cases are identified.