Viruses are obligate intracellular parasitic organisms. A virus must adhere to a living cell, enter the cell, create proteins and duplicate its genome, and then find a method to leave so that it can infect new cells. Attachment proteins in the capsid or glycoproteins embedded in the viral envelope allow a virus to connect to a specific receptor location on the host cell membrane. The host—and the cells within the host—that can be infected by a particular virus is determined by the specificity of this interaction. Despite the fact that worldwide public health demands for antiviral and vaccination products are increasing, antiviral therapies remain a difficult goal to achieve. To be successful, the industry will inevitably need to make substantial and inventive adjustments to its antiviral drug-discovery procedures.