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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

  1. Number of Norovirus, Other Etiology, or Unknown Etiology (NOU) Investigations
  2. Laboratory-based measures for NOU investigations
    1. Measure #(%) of NOU investigations with clinical specimens collected and submitted to Public Health Lab (PHL) from 2 or more people
    2. Measure #(% ) of NOU investigations where clinical specimens were tested for GI viruses at PHL
      1. #(%) of NOU investigation where specimens were tested for norovirus by RT-PCR
        1. #(%) of norovirus investigations with one or more positive specimens confirmed by PHL with sequencing & upload to CaliciNet
          1. Measure median days from first norovirus detection via RT-PCR to upload to CaliciNet
      2. #(%) of NOU investigation where specimens were tested for other viruses
    3. Measure #(%) of NOU investigations where clinical specimens were tested for pathogenic bacteria or their toxins, antigens, or specific antibodies at PHL
      1. #(%) of NOU investigation where clinical specimens were tested using culture-based diagnostics at PHL
      2. #(%) of NOU investigation where clinical specimens were tested using non-culture-based diagnostics at PHL
    4. Measure #(%) of NOU investigations where clinical specimens were tested for parasites at PHL
      1. #(%) of O/P positive clinical specimens referred to DPDx (equiv. of b.i for O/P)
  3. Measures for identified NOU investigations with epidemiologic activity or action
    1. Measure #(%) of NOU investigations with exposure assessments conducted
    2. Measure #(%) of NOU investigations where an analytic epidemiologic study was conducted
  4. Measure #(%) of NOU investigations with suspect vehicle/source identified
  5. Measure #(%) of NOU investigations with confirmed vehicle/source identified
  6. Measures for NOU investigations with identified vehicle/source where control measures or public health actions were taken
    1. #(%) of NOU investigations with exclusion of a(an) ill person(s) from high risk setting
    2. #(%) of NOU investigations with remediation or closure of an establishment linked to illness
    3. #(%) of NOU investigations with educational campaigns during outbreaks (beyond individual case education)
    4. #(%) of NOU investigations with media or public messaging (web updates, press release, etc.)
    5. #(%) of NOU investigations with regulatory action (recall, hold, etc.)
  7. Measure #(%) of 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 NOU investigations where food or environmental sample collected for testing
  9. Measure #(%) of NOU investigations where environmental health, agriculture, regulatory, or food safety program staff were contacted.
  10. Measure #(%) of NOU outbreaks where NORS form completed

Definitions

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.

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.

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)

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 testing indicates an etiologic agent, an investigation should still be classified under norovirus or other etiology, as appropriate, for NOU metrics reporting. For example, an investigation should be included in the norovirus metrics if a single specimen tests positive for norovirus and signs and symptoms of other ill people are consistent with and indicate norovirus as the suspect, or likely etiologic agent.

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.

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

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

First norovirus detection: First detection of norovirus, whether real-time or conventional RT-PCR, if both methods are utilized in the PHL.

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

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. If an investigation was originally suspected to be foodborne or point-source, but is later confirmed as person-to-person transmission, the investigation should still be included in the NOU investigations metrics.

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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