In the case of the crustacean diseases,
YHD and TS are currently considered exotic to the EU due to their
apparent absence and a lack of report of the presence in farmed or
wild susceptible species in aquatic habitats of the EU. Conversely,
WSD is listed as ‘non-exotic’ to the EU, despite a lack of published or
official reports to confirm the current or historic presence of the
causative pathogen (WSSV) in EU aquatic habitats.