What is already known about this topic? An outbreak of coronavirus disease 2019 (COVID-19) has spread throughout China and to 31 other countries and territories, including the United States.What is added by this report? Fourteen cases have been diagnosed in the United States, in addition to 39 cases among repatriated persons from high-risk settings, for a current total of 53 cases within the United States. The U.S. government and public health partners are implementing aggressive measures to slow and contain transmission of COVID-19 in the United States.What are the implications for public health practice? Interim guidance is available at https://www.cdc.gov/coronavirus/index.html. As more is learned about this virus and the outbreak, CDC w...