This 70 year old who lives in Chiba, where there is Narita International Airport (Asia’s biggest hub airport), has started showing symptom of Coronavirus infection (low grade fever) on 14th this month. Between 16~18th, she traveled by air, then she took bus tour.
That means she might have transmit her Coronavirus to hundreds (if not a thousand) of people on the plane & a tour bus. A plane & a tour bus are confined place recycling the same air all over again. Everybody breathe the same air as this Coronavirus infected woman cough and exhale.