Map

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
      .hidden {
        display: none;
    }
    div.tooltip {
        color: #222;
        background-color: #fff;
        padding: .5em;
        text-shadow: #f5f5f5 0 1px 0;
        border-radius: 2px;
        opacity: 0.9;
      position: absolute;}
  </style>
</head>

<body>
  <script>
   	var width = 700,
  		  height = 580;

var svg = d3.select( "body" )
  		.append( "svg" )
		  .attr( "width", width )
		  .attr( "height", height );

var projection = d3.geoConicConformal().center([2.454071, 46.279229]).scale(2800);

var path = d3.geoPath() // d3.geo.path avec d3 version 3
                 .projection(projection);
    
     d3.csv("GrippeFrance2014.csv", function(data) {
  	  
        
       
		d3.json("map.json", function(json) {
	    svg.selectAll("path")
           .data(json.features)
           .enter()
           .append("path")
           .attr("d", path);
      
       for (var i = 0; i < data.length; i++) {

for (var j=0; j<json.features.length;j++){
         selected=data[i].region;
              key=data[i].region;
         		if (json.features[j].properties.nom===key){    
     				 json.features[j].properties.somme2014=+data[i].somme2014
              break;
            
            }
            
         } 
       }
      var color = d3.scaleLinear().range(["white","blue"])
    	.interpolate(d3.interpolateHcl)
      .domain([0,5000]).nice();
    
      
         var tooltip = d3.select('body').append('div')
            .attr('class', 'hidden tooltip');
      
    svg.selectAll("path")
    .data(json.features)
      .style("fill", function(d) {return color(d.properties.somme2014);})
    .on('mousemove', function(d,i) {
      var mouse = d3.mouse(svg.node()).map(function(d,i) {
                        return parseInt(d);
                    });
                    tooltip.classed('hidden', false)
                        .attr('style', 'left:' + (mouse[0] + 15) +
                                'px; top:' + (mouse[1] - 35) + 'px')
                      .html(d.properties.nom + " : " + d.properties.somme2014)  ;
     
                })
       .on('mouseout', function() {
                    tooltip.classed('hidden', true);
                });
             
  
     
   })

});
  </script>
</body>

https://d3js.org/d3.v4.min.js