From 2019 to 2021, sixty age 0 herring were collected and tested for infection with viral haemorrhagic septicemia virus and viral erythrocitic necrosis virus from Port Angeles Harbor in WA, USA. This dataset describes the prevalence and intensity of infection with both pathogens. Then a series of laboratory experiments were conducted to determine how the epizootics of the two pathogens interact. This was done by conducting co-exposure and sequential exposure epizootic experiments, and measuring levels of cross-protection between the pathogens.