Horizontal mode is the likely mode of transmission when escaped subclinical infected cods or wild fishes infected by the farm, come into contact with susceptible cods from other cod farms. Disease infection will take place under stressful conditions e.g. high temperature and poor husbandry.
Qualitative Risk Assessment of the spread of nodavirus from an infected cod farm to neighbouring cod farms in a fjord system
Given the current knowledge available, the overall estimated risk for the spread of nodavirus from the infected cod farm Nærøysund A/S to the other commercial cod farms in the fjord system of Hellefjorden/Norddalsfjorden is regarded conservatively as high.