1. Release assessment
Release assessment consists of describing the biological pathway(s) necessary for an importation activity to ‘release’ (that is, introduce) a hazard into a particular environment, and estimating the likelihood of that complete process occurring. The release assessment describes the likelihood of the ‘release’ of each of the hazards under each specified set of conditions with respect to amounts and timing, and how these might change as a result of various actions, events or measures.

Examples of the kind of inputs that may be required in the release assessment are:

a) Biological factors

• Species, strain or genotype, and age of aquatic animal
• Strain of agent
• Tissue sites of infection and/or contamination
• Vaccination, testing, treatment and quarantine.

b) Country factors

• Incidence /prevalence
• Evaluation of Aquatic Animal Health Services, surveillance and control programmes, and zoning systems of the exporting country

c) Commodity factors

• Whether the commodity is alive or dead
• Quantity of commodity to be imported
• Ease of contamination
• Effect of the various processing methods on the pathogenic agent in the commodity.
• Effect of storage and transport on the pathogenic agent in the commodity.

If the release assessment demonstrates no significant risk, the risk assessment does not need to continue.

2. Exposure assessment

Exposure assessment consists of describing the biological pathway(s) necessary for exposure of humans and aquatic and terrestrial animals in the importing country to the hazards and estimating the likelihood of these exposure(s) occurring.

The likelihood of exposure to the hazards is estimated for specified exposure conditions with respect to amounts, timing, frequency, duration of exposure, routes of exposure, and the number, species and other characteristics of the human, aquatic animal or terrestrial animal populations exposed. Examples of the kind of inputs that may be required in the exposure assessment are:

a) Biological factors

• Presence of potential vectors or intermediate hosts
• Genotype of host
• Properties of the agent (e.g. virulence, pathogenicity and survival parameters).

b) Country factors

• Aquatic animal demographics (e.g. presence of known susceptible and carrier species, distribution)
• Human and terrestrial animal demographics (e.g. possibility of scavengers, presence of piscivorous birds) customs and cultural practices
• Geographical and environmental characteristics (e.g. hydrographic data, temperature ranges, water courses).

c) Commodity factors

• Whether the commodity is alive or dead
• Quantity of commodity to be imported
• Intended use of the imported aquatic animals or products (e.g. domestic consumption, restocking, incorporation in or use as aquaculture feed or bait)
• Waste disposal practices.

If the exposure assessment demonstrates no significant risk, the risk assessment should conclude at this step.

3. Consequence assessment

Consequence assessment consists of identifying the potential biological, environmental and economic consequences. A causal process should exist by which exposures to a hazard result in adverse health, environmental or socio-economic consequences. Examples of consequences include:

a) Direct consequences

• Aquatic animal infection , disease , production losses and facility closures
• Adverse, and possibly irreversible, consequences to the environment
• Public health consequences.

b) Indirect consequences

• Surveillance and control costs
• Compensation costs
• Potential trade losses
• Adverse consumer reaction

4. Risk estimation

Risk estimation consists of integrating the results of the release assessment, exposure assessment, and consequence assessment to produce overall measures of risks associated with the hazards identified at the outset. Thus risk estimation takes into account the whole of the risk pathway from hazard identified to unwanted outcome.

For a quantitative assessment, the final outputs may include:

• The various populations of aquatic animals and/or estimated numbers of aquaculture establishments or people likely to experience health impacts of various degrees of severity over time
• Probability distributions, confidence intervals, and other means for expressing the uncertainties in these estimates
• Portrayal of the variance of all model inputs
• A sensitivity analysis to rank the inputs as to their contribution to the variance of the risk estimation output
• Analysis of the dependence and correlation between model inputs.