The history of human beings is in one sense the history of war against diseases. For the purpose of controlling infectious diseases, our research and education focuses on the transmission, proliferation and replication mechanisms of pathogens, including bacteria, prion and viruses. Especially, we aim to clarify how the production of prion protein is regulated and how the double-strand RNA viruses, such as Ibaraki virus, replicate efficiently. To answer these questions, we analyze pathogens from different aspects, ecology, epidemiology and molecular biology.