A control zone has been established around the site containing 26 farms of which 18 have been emptied and eight are still stocked.
There are a further 14 farms in the surveillance zone of which four still have fish stocks.
The Fisheries Research Service said that all of the fish farm sites are being inspected by staff from the FRS Fish Health Inspectorate, with further samples being taken from some of those sites, to establish the current situation on each site.
There are 40 registered fish farming sites in the south west Shetland management area, although not all of these sites are currently holding fish.
All sites holding species susceptible to, or able to act as a vector for ISA virus will require to be fallowed (emptied of stock), cleaned and disinfected before being restocked. The length of this fallow period will vary depending upon a site by site risk evaluation.
A spokeswoman for the Fisheries Research Service told TheFishSite that the investigation into the cause of the outbreak was ongoing and that to date there had been no further outbreak.
However, she added that the cause might never be discovered.
Still no Source for ISA Outbreak
SHETLAND - Investigations are continuing into the outbreak of Infectious Salmon Anaemia at a fish farming site in the south west of Shetland, but experts are no nearer to finding the cause of the outbreak.
