Rheumatic fever is most commonly caused by:

• septicemia
O mononucleosis
• herpes zoster
• streptococcus pyogenes

The correct answer is streptococcus pyogenes. Rheumatic fever is an inflammatory disease that can develop after an untreated streptococcal infection, specifically caused by the bacteria Streptococcus pyogenes.

Rheumatic fever is most commonly caused by streptococcus pyogenes.