herpes simplex vs syphilis

herpes simplex

noun
  • A viral disease caused by Human herpesvirus 1 or Human herpesvirus 2 in genus Simplexvirus. 

syphilis

noun
  • A disease spread via sexual activity, caused by the bacterium Treponema pallidum. 

How often have the words herpes simplex and syphilis occurred in a corpus of books? (source: Google Ngram Viewer )