Dietary consumption of fish is widely recommended because of the beneficial effects of omega-3 polyunsaturated fatty acids on the risks of cardiovascular and Alzheimer's diseases. The American Heart Association currently recommends eating at least two servings of fish per week. We are concerned that consumption of farmed fish may provide a means of transmission of infectious prions from cows with bovine spongiform encephalopathy to humans, causing variant Creutzfeldt Jakob disease.