This example displays a horizontal bar chart of COVID-19 case counts for 20 countries using React and D3 v5. The visualization maps each country to a green rectangle, with bar lengths proportional to population values fetched from a remote CSV file. It uses `d3.csv` for data loading, `scaleBand` and `scaleLinear` for positioning, and renders gridlines with axis ticks directly as SVG elements. The React component manages data state with `useState` and `useEffect`, while D3 handles scaling and tick generation.