Question

Once syphilis enters its third stage, it is no longer curable

Answer 1

Hi. Syphilis has four stages, primary, secondary, inactive and late. The third stage begins when the symptoms from the first and second stage disappear. During this stage, the infection lives in your body, however, you may not show any symptoms. 

You can find further information on the Women's Health(dot)gov site. Hope this helps.

Take care,
Diana