The present application provide novel iminosugars and their use in treatment of viral infections, such as Dengue infection and Influenza A infection. The present inventors discovered certain deoxynojirimycin derivatives may be effective against one or more viruses, which may be, for example, a Dengue virus and/or a virus belonging to the Orthomyxoviridae family, such as an Influenza A virus. In particular, such deoxynojirimycin derivatives may be useful for treating a disease or condition caused by or associated with one or more viruses. In certain embodiments, the deoxynojirimycin derivatives may increase a survival rate or probability for a subject infected with one or more viruses, which may be, for example, a Dengue virus and/or a virus belonging to the Orthomyxoviridae family, such as an Influenza A virus.