Both humans and animals are susceptible to infections caused by the poxvirus family of viruses. Smallpox (variola), monkeypox, vaccinia, and cowpox are examples orthopoxviruses. Naturally occurring smallpox was eradicated worldwide in the late 1970s. However, smallpox remains a concern as a potential agent of bioterrorism since it is highly contagious, a large proportion of the population has no immunity, and there is little available vaccine. Emerging infections such as monkeypox also pose a concern to human health. In this presentation, Inger K. Damon, M.D., Ph.D., acting chief of the Poxvirus and Rabies Branch and chief of the Poxvirus Program in the Division of Viral and Rickettsial Diseases at the Centers for Disease Control and Prevention, will address these and other emerging pathogen and bioterrorism threats of poxviruses.