What is Needed to Conduct a Good Risk Assessment

Qualitative vs. Quantitative Risk Assessment Approaches

Risk assessors may proceed by using qualitative and/or quantitative approaches. Often risk assessments include a combination of both. A key principle in both approaches is transparency, sharing the information with all interested parties.

The qualitative approach primarily uses categorical values for inputs and outputs. The input variables are defined categorically (such as low, medium or high or in binary terms by assigning a value of 0 or 1). These categorical inputs are then processed systematically to determine a categorical output (such as low, medium, or high risk) or, in some cases, a numerical output (though the result is still technically qualitative).

Example of a Qualitative Assessment
Scope of the analysis

The risk of introduction of Newcastle Disease virus from importation of fresh and frozen poultry meat and other poultry products from Federally inspected slaughtering plants in certain states of a country. Other states in the country were known to have Newcastle Disease.

Information submitted: the states requesting permission to import products submitted information on:

• veterinary authority, organization, and infrastructure;
• surveillance and control mechanisms for disease;
• diagnostic laboratory capabilities;
• disease outbreak history and prevalence in the states in question, as well as adjacent states;
• disease control programs;
• vaccination status, separation of the region from regions of higher risk through physical or other barriers;
• control mechanisms for moving animals and products from regions of higher risk;
• livestock demographics and marketing practices;
• animal health policies and infrastructure for animal disease control in the region.

The quantitative approach provides numerical scales for input and output values, such as a number expressing a probability that there will be an outbreak in a defined period of time or per unit of commodity (e.g., such as fruit flies per number of oranges). It may involve:

• Asking precise questions about activity and outcome;
• Developing mathematicals model linking activity and outcome;
• Obtaining evidence pertaining to the model;
• Assigning quantitative values to the model;
• Calculating outcomes;
• Submitting for peer review.

REMINDER: The examples relating to animal and animal products are subject to the regionalization regulation covered in Module 2. APHIS responds to requests from foreign countries to recognize areas as free from a particular foreign animal disease or diseases or some other defined category of risk for importation of that disease. APHIS does not perform a risk assessment for importation of a single shipment of animals or a commodity.

Example of Quantitative Assessment
Scope of the analysis
The risk of introduction in the U.S. of classical swine fever (hog cholera) from importation of fresh and frozen pork products intended for human consumption from commercial hog operations processed at federally inspected slaughter facilities from certain states in a foreign country. The country of origin was one that was known to have classical swine fever in states other than the ones requesting permission to import.

Data Analysis
Data was submitted from commercial swine operations in the states in question. Analysis focused on surveillance and monitoring activities and included probability estimates of the amount of material to be imported, the likelihood that material would be contaminated, and the possibility that contaminated material would infect U.S. livestock.

Typical of many situations, a qualitative assessment also was conducted for the classical swine fever example cited above. It considered all of the factors listed under the qualitative risk assessment example.