Our primary data source is DXY, an online platform run by members of the Chinese medical community, which aggregates local media and government reports to provide COVID-19 cumulative case totals in near real-time at the province level in China and country level otherwise. Every 15 minutes, the cumulative case counts are updated from DXY for all provinces in China and affected countries and regions. For countries and regions outside mainland China (including Hong Kong, Macau and Taiwan), we found DXY cumulative case counts to frequently lag other sources; we therefore manually update these case numbers throughout the day when new cases are identified. To identify new cases, we monitor various twitter feeds, online news services, and direct communication sent through the dashboard. Before manually updating the dashboard, we confirm the case numbers using regional and local health departments, namely the China CDC (CCDC), Hong Kong Department of Health, Macau Government, Taiwan CDC, European CDC (ECDC), the World Health Organization (WHO), as well as city and state level health authorities. For city level case reports in the U.S., Australia, and Canada, which we began reporting on February 1, we rely on the US CDC, Government of Canada, Australia Government Department of Health and various state or territory health authorities. All manual updates (outside mainland China) are coordinated by a team at JHU.