“…In a nationwide survey conducted by the MHLW on August 12–13, 2020, using a social networking service, 82.5% of the more than 15 million respondents reported that they were thoroughly wearing masks as a COVID-19 countermeasure ( LINE Corporation, 2020 ). Wearing a mask has been found to increase body temperature near the face, and may also make breathing difficult and increase heart and respiratory rates ( Yokobori, 2020 ; Johnson, 2016 ; Samannan et al, 2020 ), and we hypothesize that the habit of wearing masks in the ‘new normal’ may contribute to an increased risk of heat illness in the summer ( NHK, 2020 ). An increase in the number of heat illness-related emergency transferees and visits to medical institutions could place additional burdens on medical institutions dealing with new coronavirus infections.…”