# Commission Delegated Regulation (EU) 2020/689 of 17 December 2019 supplementing Regulation (EU) 2016/429 of the European Parliament and of the Council as regards rules for surveillance, eradication programmes, and disease-free status for certain listed and emerging diseases (Text with EEA relevance), Division 2: The restricted zone must have been defined on a case-by-case basis taking into account factors influencing the risks for the spread of WSSV to farmed and wild crustaceans, such as:

Extent: E+W+S+N.I.

(i) the number, age, rate and distribution of the mortalities of crustaceans on the establishment or group of establishments infected with WSSV including other establishments and wild crustaceans;
(ii) the distance to and density of neighbouring establishments or groups of establishments including wild crustaceans;
(iii) the proximity to processing establishments, contact establishments or groups of establishments;
(iv) the species, especially susceptible species and vector species, present at the establishments or groups of establishments;
(v) the farming practices applied in the affected and neighbouring establishments and groups of establishments;
(vi) the hydrodynamic conditions; and
(vii) other factors of epidemiological significance identified.
Table 6. A
Scheme for Member States, zones and compartments for the 2-year control period which precedes the achievement of status free from infection with WSSV
Year of surveillance
Number of health visits per year to each establishment or group of establishments
Number of laboratory examinations per year
Number of crustaceans in the sample
Year 1
1
1
150
Year 2
1
1
150

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Source: https://www.legislation.gov.uk/eur/2020/689/annex/VI/chapter/6/section/3/division/2 (the official version)
Page: https://openlegislation.uk/eu-regulation-2020-689/annex-VI/chapter-6/section-3/division-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.