It's important so that they know exactly where the disease started. Knowing who patient zero is helps them to identify who that person interacted with. From there, they can determine where the disease spread to. This will aid them in stopping the disease before it spreads any further.
People who have darker skin have more melanin which is a black or dark brown pigment in the skin. When we are out in the sun our skin produces more melanin, which helps our skin be more resistant in the sun. This is why we tan.
