function handleMouseOver(d) {
d3.select(this)
.style("opacity", 0.8)
.style("stroke", "#000000")
.style("stroke-width", 2);
tooltip.transition().duration(200).style("opacity", 0.9);
let name = d.properties.NAME;
let lookup = mapData.find((o) => o.name === d.properties.NAME);
let cases = lookup.casesPer100k;
let rate = lookup.positivityRate;
tooltip
.html(
`${name} County:<br />Average test positivity rate: ${rate}<br />Average per capita case rate: ${cases}`
)
.style("left", `${d3.event.pageX + 20}px`)
.style("top", d3.event.pageY - 45 + "px");
}