This horizontal tree diagram visualizes a hierarchy of global health data, tracing from a "Global Health" root through four countries (Canada, Japan, Germany, Kenya) into disease categories and specific illnesses. Node colors encode the tree depth, with a legend distinguishing global health, country, category, and disease levels. The code uses D3 v7’s `d3.hierarchy` and `d3.tree` layout, drawing links with `d3.linkHorizontal` and rendering nodes as SVG circles and text labels. Styling is minimal, relying on CSS classes for links and nodes.