When Smoker encountered Trafalgar Law at Punk Hazard , he demanded answers from Law, some regarding on who Law was working for, indicating a hidden agenda.  They battled each other, Law managed to gain the upper hand by stealing Smoker's heart with his Mes attack. While Smoker yielded in defeat, Law commented that he does not have to tell him anything.  Law also switched Smoker’s and Tashigi's personalities in their bodies.  However, Smoker and Tashigi form a temporary alliance with the Straw Hat Pirates and Trafalgar Law in order to defeat Caesar Clown and Vergo on the condition that they do not mention Law or Joker's complicity to the Marines. 
Later as the syndrome becomes more wide spread, it is learned that the syndrome is not passed as a virus but as sensory data. Simply being around a devil beast and experiencing it with any of the five senses is enough to become one. Additionally, being around a particular devil beast for a long amount of time will make a person become a devil beast of similar design (for example, Kazumi grew wings almost exactly like Jun's). It also becomes apparent that simply becoming a devil beast is not enough to make one act monstrous, and that the ones Jun was forced to dispatch were merely more volatile individuals incapable of accepting their change.