A radial tree visualization shows the hierarchical distribution of COVID-19 cases, with nodes representing top infected regions branching outward from a central root. The layout uses d3.cluster() to arrange nodes in a circular pattern, with each branch's position and length encoding the case counts loaded from data.csv. The visualization is rendered as an SVG with animation, using d3.hierarchy() to structure the data and d3.nest() to group entries by multiple categorical levels. React provides the component framework for this interactive chart.