Decreased Influenza Activity During the COVID-19 Pandemic - United States, Australia, Chile, and South Africa, 2020. - Olsen, Sonja J.; Azziz-Baumgartner, Eduardo; Budd, Alicia P.; Brammer, Lynnette; Sullivan, Sheena; Pineda, Rodrigo Fasce; Cohen, Cheryl; Fry, Alicia M. (MMWR: Morbidity & Mortality Weekly Report, 2020)