In 2003, the U.S. Centers for Disease Control and Prevention (CDC) responded to U.S. outbreak of monkeypox, the first human monkeypox outside of Africa. Scientists at the Marshfield Clinic in Marshfield, Wisconsin, recovered a virus resembling a poxvirus from one of the first patients and the patientﾒs pet prairie dog. CDC lab tests ﾗincluding several PCR-based assays and gene sequencingﾗconfirmed that the agent causing the illnesses was monkeypox virus. Investigators determined that a shipment of animals from Ghana, imported to Texas on Apr. 9, 2003, introduced monkeypox virus from the West African genetic group (clade) into the U.S.