Centers for Disease Control and Prevention (CDC) director Dr. Julie L. Gerberding said Thursday that she thinks that the monkeypox outbreak can be contained in the United States by tracing infected animals and isolating humans. She noted that the CDC is aggressively investigating the animal sources linked to the outbreak. The disease is believed to have come into the country via a Gambian giant rat from West Africa, and was transmitted to prairie dogs sold as pets. Health officials are investigating 87 cases in six states, with 20 confirmations of viral infection, and Gerberding says that all cases are thought to have resulted from exposure to infected pets; person-to-person transmission does not seem to have occurred. According to Gerberding, at least 20 of those exposed to monkeypox have been given smallpox vaccinations, since these can also protect against monkeypox.