A choropleth map displays confirmed COVID-19 cases per country, colored by an ordinal scale using D3's `scaleOrdinal` and `schemeSpectral`. The map uses `geoNaturalEarth1` projection with `geoPath` to render SVG country shapes from TopoJSON, with data loaded from a CSV file. Users can zoom and pan via D3's `zoom` behavior, and clicking a legend item highlights matching countries while dimming others.