Another Salmon farm is Quarantined

Again we hear news that Salmon has been infected with a disease. Its sad that the salmon may be dying off even if the disease does not affect humans. I wonder if the disease is natural or if the environment of the salmon farm is what is fostering the disease. I want to know if people think that the farms are what are causing the disease. I also want to know if getting rid of the farms will help the salmon become more healthy. I suppose that salmon weren't tested for diseases as often as they are now that they are in captivity, so I wonder if they had these diseases before.