AdvertisementThe riddle of Japan's dramatic drop in COVID numbersDecember 20, 2021Anthony KuhnfacebookEmailCommuters wear masks to help curb the spread of the coronavirus during rush hour at the Shinagawa train station in Tokyo on Oct. 1. Case numbers have dropped significantly in Japan since summer. Researchers are trying to determine why. One theory is that the willingness to wear masks has made a difference; other theories are being investigated. (Eugene Hoshiko/AP)