COVID-19 is a public health official's "worst nightmare," Dr. Anthony Fauci, the nation's leading infectious disease doctor, said Thursday. "What is the worst nightmare that a public health official could have and what are the things that we fear the most?" Fauci said. "The answer is consistent among me and my colleagues: The emergence of a respiratory illness that is highly transmissible it its efficiency of going from person to person that has a significant degree of morbidity and mortality." "Unfortunately for our planet, that's exactly where we are right now, with this now historic COVID-19 pandemic," he said.