Why do you call Endometriosis a "silent epidemic"?

Why do you call Endometriosis a "silent epidemic"?

There are approximately diagnosed pathologically close to six million women in United States with endometriosis.  I like to say endometriosis has a component of silent epidemic.  There are probably another two to three million women on top of it, not ever diagnosed.  These women are either missed through their infertility complaints and problems or they do not have symptoms or their symptoms are being overlooked as other diseases.  It may be more but certainly the number is not only 6 but it is above that.  That is why I called endometriosis a silent epidemic.

What are the most prominent physical symptoms of Endometriosis, and how do these affect women physically and emotionally?