Aquaculture is rapidly growing in economic importance in the USA, where California (CA) is considered as an emergent leader aquaculture industry worth an estimated $110 million per year. The primary aquaculture species in the state are salmonids, particularly Oncorhynchus sp. However, these fish are affected by many endemic infectious agents such hematopoietic necrosis virus (IHNV), cutthroat trout virus (CTV), bacterial kidney disease (BKD), Flavobacterium columnare and F. psychrophilum. Some of those agents, such as IHNV, are notifiable to the World Animal Health Organization (OIE) and are responsible for high mortality and significant socio-economic losses in hatchery stocks and wild salmonids in fresh waters. The spread in these diseases has been facilitated by a limited information on the virus distribution, poor knowledge on risk factors, and the lack of an adequate surveillance system. In line with the priorities of the United States Aquatic Animal Health Plan, and with CFAH high priority issues, this project will address a key problem of national importance by analyzing historical monitoring data to identify risk factors for disease occurrence and by developing a prototype for a near real-time surveillance system for fish diseases in CA.