A world map visualization traces the spread of COVID-19 by drawing arcs and circles between countries. It shows the progression of the outbreak over time, with each circle representing a country's reported cases and each line indicating a transmission route from one nation to another. The visualization uses d3.geoNaturalEarth1 for the map projection, d3.geoPath for rendering country boundaries, and d3.scaleSqrt for sizing circles based on case counts. Data is loaded from two CSV files containing origin and destination coordinates, which are combined to create the curved connection paths.