My earlier worst fears confirmed: Younger adults were the main source of 61 different outbreak clusters in Japan. In this study (in a CDC journal), contact tracing isolated the primary source of 61 epidemic clusters to be mostly younger adults! 🧵 #COVID19 https://t.co/PbIQUnDXV0 pic.twitter.com/3uKvUuUaNZ

— Eric Feigl-Ding (@DrEricDing) June 14, 2020