CURRENT ISSUEONE OF THE BASIC CONCEPTS OF ECOLOGY IS THAT ORGANISMS MAY BECOME SPECIALISTS OR GENERALISTS, DEPENDING ON ENVIRONMENTAL CONDITIONS. THIS IS TRUE FOR VIRUSES, WHICH MAY INFECT AND CAUSE DISEASE IN ONLY ONE HOST SPECIES (SPECIALIST) OR USE MULTIPLE HOST SPECIES (GENERALIST). THERE ARE MANY THEORETICAL PREDICTIONS ABOUT SPECIALIST OR GENERALIST VIRUSES, BUT WE HAVE FEW EXAMPLES OF ANIMAL VIRUSES IN WHICH BOTH GENERALIST AND SPECIALIST STRAINS HAVE EVOLVED NATURALLY. THIS RESEARCH WILL PROVIDE AN EXCEPTIONALLY WELL-STUDIED SYSTEM FOR TESTING PREDICTIONS OF THE GENERALIST-SPECIALIST THEORY IN AN AQUATIC VIRUS OF SALMON AND TROUT. THIS RESEARCH WILL DIRECTLY IMPROVE THE UNDERSTANDING AND MANAGEMENT OF ONE OF THE MOST IMPORTANT SALMONID PATHOGENS IN THE PACIFIC NORTHWEST, INFECTIOUS HEMATOPOIETIC NECROSIS VIRUS (IHNV). A MISSING LINK IN THE CONTROL OF IHNV HAS BEEN A LIMITED UNDERSTANDING OF HOW THIS VIRUS IS TRANSMITTED WITHIN AND BETWEEN SALMON SPECIES. THE DEMAND FOR THIS KNOWLEDGE IS HIGH AMONG MANAGERS. THE SALMONID SPECIES THAT ARE IMPACTED BY IHNV HAVE VAST CULTURAL, CONSERVATION, AGRICULTURAL, AND FISHERIES IMPORTANCE, AND ENHANCED CONTROL OF THE VIRUS IS A PRIMARY OBJECTIVE OF STATE, FEDERAL, AND TRIBAL AGENCIES. ULTIMATELY, REDUCTION IN IHNV BURDEN WOULD PROVIDE SIGNIFICANT ECONOMIC AND ECOLOGICAL BENEFITS. AS SUCH, THE RESEARCH GROUP HAS ESTABLISHED PRODUCTIVE PARTNERSHIPS WITH STAKEHOLDER GROUPS IN THE PACIFIC NORTHWEST, INCLUDING TRIBAL, STATE AND FEDERAL MANAGERS AND SCIENTISTS. THIS PROPOSAL ALSO OFFERS A TRANSLATIONAL MODEL AND FRAMEWORK FOR UNDERSTANDING DISEASE TRANSMISSION OF OTHER AQUATIC AND TERRESTRIAL HOST-PATHOGEN SYSTEMS THAT SHOW VARIATION IN SPECIES SPECIALIZATION. THE PROPOSED PROJECT WILL TRAIN STUDENTS, TECHNICIANS, AND POSTDOCS IN HIGHLY SOUGHT AFTER SKILLS IN MOLECULAR BIOLOGY, MICROBIOLOGY, AND DISEASE MODELING. A HIGH PRIORITY WILL BE GIVEN TO TRAINING INDIVIDUALS FROM UNDER-REPRESENTED OR DISADVANTAGED GROUPS. THE PROJECT WILL ALSO DEVELOP SEVERAL OUTREACH ACTIVITIES TO INCREASE PUBLIC AWARENESS ABOUT ISSUES SUCH AS DISEASE TRANSMISSION, EVOLUTION, AND MANAGEMENT, AND CONTINUE ONGOING RELATIONSHIPS WITH MUSEUMS AND EDUCATIONAL GROUPS. THE EFFICACY OF THESE OUTREACH ACTIVITIES WILL BE EVALUATED THROUGH PARTICIPANT SURVEYS AND FOLLOW-UPS. LASTLY, THE PROJECT IS BUILT ON INTERDISCIPLINARY TIES ACROSS FIVE INSTITUTIONS AND BETWEEN ACADEMIC AND GOVERNMENT SECTORS. THIS TYPE OF INTEGRATED RESEARCH NETWORK IS CRITICAL FOR THE SUCCESSFUL MANAGEMENT OF THE INCREASINGLY COMPLEX INFECTIOUS DISEASE PROBLEMS PLAGUING SOCIETY.METHODS AND APPROACHESRESEARCH WILL INTEGRATE FIELD DATA ON VIRUS INCIDENCE IN PACIFIC NORTHWEST SALMONID FISHES AND LABORATORY EXPERIMENTS TO DETERMINE HOW THE VIRUS INFECTS, REPLICATES AND TRANSMITS BETWEEN DIFFERENT SALMON SPECIES, AS WELL AS DIFFERENCES IN HOW THREE SALMON SPECIES RESPOND TO THE GENERALIST AND SPECIALIST STRAINS OF IHN VIRUS. WE WILL THEN USE INFORMATION FROM THESE STUDIES INMATHEMATICAL MODELS OF VIRUS DISEASE, WHICH WILL BE USED TO GAIN A MECHANISTIC UNDERSTANDING OF HOW GENERALIST AND SPECIALIST STRAINS ARE TRANSMITTED ACROSS DIFFERENT SPECIES. OUR SPECIFIC OBJECTIVES ARE TO;QUANTIFY AND EVALUATE THE VARIABILITY IN INFECTIOUSNESS, SUSCEPTIBILITY, AND RECOVERY BETWEEN VIRUS THAT SPECIALIZE IN ONE SALMON SPECIES VERSUS THOSE THAT INFECT MANY SPECIES,EXAMINE THE IMPORTANCE OF CROSS- SPECIES TRANSMISSION FOR EACH VIRUS SUBGROUP, ANDDEVELOP A MATHEMATICAL MODEL TO UNDERSTAND THE TRANSMISSION OF GENERALIST AND SPECIALIST VIRUSES IN DIFFERENT SALMON SPECIES, FOUND ACROSS THE COMPLEX LANDSCAPE OF THE COLUMBIA RIVER BASIN IN THREE PACIFIC NORTHWEST STATES.OUR ULTIMATE GOAL IS TO DEVELOP A FRAMEWORK FOR UNDERSTANDING THE LANDSCAPE EPIDEMIOLOGY OF GENERALIST AND SPECIALIST VIRUSES IN AN AQUATIC ECOSYSTEM, WITH RELEVANCE TO OTHER AQUATIC DISEASES AND OTHER VIRUSES OF VERTEBRATES, INCLUDING MAMMALS . THIS INFORMATION CAN BE USED GENERALLY TO TEST THEORY ON FACTORS AFFECTING EVOLUTION OF GENERALIST AND SPECIALIST VIRUSES, AND TO INFORM DISEASE MANAGEMENT DECISIONS FOR PACIFIC NORTHWEST SALMONID FISH HEALTH.