KPop Fandoms drive COVID-19 Public Health Messaging on Social Media.

This report examines an unexpected but significant source of positive public health messaging during the COVID-19 pandemic -- K-pop fandoms. Leveraging more than 7 million tweets related to mask wearing and K-pop between March 2020 and March 2021, we analyzed the online spread of the hashtag \#WearAMask amid anti-mask sentiments and public health misinformation. Analyses reveal the South Korean boyband BTS as the most significant driver of health discourse. Tweets from health agencies and prominent figures that mentioned K-pop generate 111 times more of online response compared to tweets that did not. These tweets also elicited a strong responses from South America, Southeast Asia, and rural States -- areas often neglected in Twitter-based messaging by mainstream social media campaigns. Our results suggest that public health institutions may leverage pre-existing audience markets to synergistically diffuse and target under-served communities both domestically and globally, especially during health crises such as COVID-19.