chancroid vs sexually transmitted infection

chancroid

noun
  • A sexually transmitted infection, caused by bacteria of species Haemophilus ducreyi, characterized by painful sores on the genitalia. 

  • A sore characteristic of this infection. 

sexually transmitted infection

noun
  • A sexually transmitted disease, with or without symptoms. 

How often have the words chancroid and sexually transmitted infection occurred in a corpus of books? (source: Google Ngram Viewer )