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Norovirus, Other Etiology, or Unknown Etiology (NOU) Metrics

The FoodCORE performance metrics are a list of measurable activities covering diverse aspects of outbreak response. These activities span from outbreak surveillance and detection through investigation, response, control, and prevention measures. Using the metrics, each center provides data about the burden, timeliness, and completeness of foodborne disease activities related to the key areas of activity.

Metrics in bold represent the minimum reporting requirements for FoodCORE Centers

NOU Metrics

1a. Total number of all Norovirus, Other Etiology, or Unknown Etiology (NOU) Investigations

1b. Total number of foodborne or point-source NOU investigations

1c. Total number of person-to-person NOU investigations

 

Laboratory-based Metrics for all NOU investigations

2a. Measure #(%) of all NOU investigations with clinical specimens collected and submitted to the Public Health Lab (PHL)

2b. Measure #(%) of all NOU investigations where submitted clinical specimens  were tested for GI viruses at the PHL  

  • 2b.1. Measure #(%) of all NOU investigations where GI viral testing of specimens included testing for norovirus by real-time RT-PCR at the PHL
    • 2b.1.1. Measure #(%) of all NOU investigations with two or more specimens confirmed positive for norovirus by RT-PCR at the PHL where at least one specimen was sequenced and uploaded to CaliciNet
      • 2b.1.1.1. Measure median days from first norovirus detection at the PHL via RT-PCR to upload of sequence to CaliciNet
  • 2b.2. Measure #(%) of all NOU investigations where GI viral testing of specimens included  testing for other viruses (e.g., sapovirus, astrovirus, rotavirus, adenovirus) at the PHL

2c. Measure #(%) of all NOU investigations where clinical specimens  were tested for pathogenic bacteria or their toxins, antigens, or specific antibodies at the PHL

  • 2c.1. Measure #(%) of all NOU investigations where bacterial testing of specimens included culture-based diagnostics at the PHL
  • 2c.2. Measure #(%) of all NOU investigations where bacterial testing of specimens included non-culture-based diagnostics at the PHL

2d. Measure #(%) of all NOU investigations where clinical specimens  were tested for parasites at the PHL

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Investigation-based Metrics

Metrics for identified foodborne or point-source NOU investigations with epidemiologic activity or action

3a. Measure #(%) of foodborne or point-source NOU investigations with exposure assessments conducted

3b. Measure #(%) of foodborne or point-source NOU investigations where an analytic epidemiologic study was conducted

4. Measure #(%) of foodborne or point-source NOU investigations with suspect vehicle/source identified

5. Measure #(%) of foodborne or point-source NOU investigations with confirmed vehicle/source identified

6a-e. Measures for foodborne or point-source NOU investigations with an identified vehicle/source where control measures or public health actions were taken

  • Measure #(%) of foodborne or point-source NOU investigations with exclusion of an ill person(s) from high risk setting
  • Measure #(%) of foodborne or point-source NOU investigations with remediation or closure of an establishment linked to illness
  • Measure #(%) of foodborne or point-source NOU investigations with educational campaigns during outbreaks (beyond individual case education)
  • Measure #(%) of foodborne or point-source NOU investigations with media or public messaging (web updates, press release, etc.)
  • Measure #(%) of foodborne or point-source NOU investigations with regulatory action (recall, hold, etc.)

7. Measure #(%) of foodborne or point-source NOU investigations with link to a common location of exposures (e.g., restaurant, food establishment, nursing home, etc.) where an on-site environmental health assessment was conducted 

8. Measure #(%) of foodborne or point-source NOU investigations where food or environmental sample was collected for testing 

9. Measure #(%) of foodborne or point-source NOU investigations where environmental health, agriculture, regulatory, consumer protection, or food safety program staff were contacted

 

Outbreak-based Metrics

10. Measure #(%) of all NOU outbreaks where NORS form was completed

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Definitions

Other Etiology:  Enteric illness with determined etiology that is not Salmonella, Shiga toxin-producing Escherichia coli, Listeria, or norovirus.   

Unknown Etiology:  Enteric illness with no determined/identified etiology from any of the case, product, or environmental testing to indicate the etiologic agent.  This can be because no specimen or sample yielded an isolate or other positive result, and would also include investigations where no specimens or samples were collected.

Foodborne or Point-source Norovirus, Other Etiology, or Unknown Etiology (NOU) Investigation: Epidemiologic activity in response to cases where there is indication of non-person-to-person transmission of a similar enteric illness.  This includes investigations where there are demographic or epidemiologic indications of a common, point-source of infection even without laboratory subtyping data to link cases.

Specimens: This will include all clinical specimens submitted to PHL.

Samples: This will include all non-clinical, samples (food, environmental, etc.) submitted to PHL.

Exposure assessment: To include an interview (of any format) that assesses exposures prior to onset of illness, via an open-ended exposure history, or via a list of potential exposures.  The key factor to be considered an exposure history is an interview that goes beyond assessment of high-risk settings and prevention education to ascertain food consumption/preference, or other exposure data.

Analytic epidemiologic study:  A systematic, statistical analysis against a comparison group or within a cohort to test a hypothesis

Suspect norovirus or other etiology outbreak: If there are not sufficient specimens or samples to classify an outbreak as a confirmed norovirus or other etiology, but the available data (testing, epidemiologic data such as signs, symptoms, and incubation period) indicate an etiologic agent, an investigation should still be classified under norovirus or other etiology, as appropriate, for NOU metrics reporting. 

Confirmed norovirus outbreak:  Outbreak with two or more clinical specimens positive for norovirus by RT-PCR, EM, or EIA.

Confirmed other etiology outbreak:  For most etiologic agents, CDC considers an outbreak to have a confirmed etiology if there are two or more lab-confirmed cases. However, in botulism, marine toxins, and other chemical outbreaks, the definition of a confirmed etiology is not as strict. Since botulism, marine toxins, and other chemical outbreaks have such distinct clinical symptoms, a physician's diagnosis is often sufficient and laboratory confirmation is not necessary. Therefore, for such outbreaks, CDC would consider it a confirmed etiology outbreak if there is at least 1 probable case (based on clinical symptoms).  (See also: Other Etiology definition above)

All measurements of time are in median days: Measurements will exclude weekend days.  For laboratory time measurements, only isolates subtyped at the PHL should be included. 

Vehicle/source Identified:

SUSPECT vehicle/source investigations: Investigations of infection where investigational and/or laboratory data indicate a likely vehicle/source of infection without confirmation:  vehicle/source is a known risk factor, established errors in food preparation, or reported consumption by a high proportion of cluster-associated cases.
CONFIRMED vehicle/source investigations:  Investigations of infection where the etiologic agent has either been identified from the vehicle/source, or the vehicle/source has been statistically implicated in an analytic study.

Control measure: to include interventions such as exclusion of an ill person(s) from high risk setting, remediation or closure of an establishment linked to illness, educational campaigns during daycare outbreaks, etc.  To be considered a control measure, activities should extend beyond the routine educational component of an interview or exposure assessment.

Public health action: to include media, public messaging (web updates, press release, etc.), or regulatory action (recall, hold, etc.).  To be considered a public health action, activities should extend beyond the routine investigation activities and reach at-risk individuals beyond identified cases.  A public health action should be included in the NOU metrics if the FoodCORE Center was directly involved in the action, or is aware that a public health action was taken during a multijurisdictional investigation.  For example, if CDC produces public messaging during a multistate outbreak investigation that a FoodCORE Center is involved in, that investigation would be associated with a public health action for the purposes of the metrics.

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