That cruise ship didn't issue masks until after the outbreak had occurred: "The first recorded fever on board the ship was a febrile passenger on day 8. Isolati

That cruise ship didn't issue masks until after the outbreak had occurred: "The first recorded fever on board the ship was a febrile passenger on day 8. Isolation protocols were immediately commenced, with all passengers confined to cabins and surgical masks issued to all. Full personal protective equipment was used for any contact with any febrile patients, and N95 masks were worn for any contact with passengers in their cabins. The crew still performed duties, including meal services to the cabin doors three times a day, but rooms were not serviced. Expedition staff helped with crew duties at meal service." So passengers were already infected when that 81% figure was computed. https://thorax.bmj.com/content/75/8/693 https://thorax.bmj.com/content/75/8/693 In a village in Tuscany, over 3000 people were actively tested and 50-75% were asymptomatic: https://www.bmj.com/content/368/bmj.m1165 https://www.bmj.com/content/368/bmj.m1165 And among NYC labor and delivery patients, 88 percent were asymptomatic: https://www.washingtonpost.com/outlook/2020/04/20/we-tested-all-our-patients-covid-19-found-lots-asymptomatic-cases/ https://www.washingtonpost.com/outlook/2020/04/20/we-tested-... This number is not at all unusual in the general population, regardless of mask wearing.