By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) - Over the past ten years the rates of a sexually transmitted disease, thought to be a thing of the past, have been on the rise.  I am talking about syphilis.

Syphilis is caused by an organism called treponema pallidum and is spread through sexual contact. One of the biggest problems is that syphilis is not particularly easy to diagnose.

From a lab standpoint there can be a several week delay between infection and the development of an immune response.  This means that people can be tested and actually have syphilis but believe that they do not actually have it.

This is all a dramatic change becuse back in 2000 the rates of syphilis were at an all time low. If this is not bad enough, syphilis can be spread to an unborn baby and this rate has increased by 23 percent.