The United States is reporting some of the highest number of cases and deaths from the Coronavirus Disease 2019 (COVID-19) pandemic globally, and the disease is affecting communities nationwide. In response, federal, state, and local governments have undertaken containment and mitigation efforts to "flatten the curve" --that is, to slow widespread transmission that could overwhelm the nation's health care system and to reduce spread of the disease while treatments and vaccines are being developed that will lessen the health impact of the virus. This book provides answers to numerous questions related to COVID-19 testing, including types of testing available and their reliability. It also discusses basic principles of contact tracing to stop COVID-19 transmission.