Special Accidents like The Rabies Outbreak are time-limited challenges, and they will be considered seasonal events. They will show up in your game after reaching some milestones in your hospital. If you haven't got them yet, NO WORRIES! All players will have the opportunity of playing the Special Accidents. They will definitely show up when your hospital is ready.  
Would you like more Special Accidents? Stay tuned! The team is actively working on adding more content.