According to the Old Testament, you would become unclean if a hemorrhaging person touched you (Lv 15:25-33). If you touched a dead person, you would also become unclean (Nm 19:11ff). An unclean, defiling power seemed to come forth from the bleeding or dead.
However, when Jesus was touched by or touched the unclean, an unclean power did not defile Him. Instead, His healing, life-giving power went out from Him and made the unclean clean. Unlike everyone else, Jesus is contagious in the good sense.
For instance, if you put a healthy person in a room of sick people, do all the sick people catch health or does the healthy person get sick? Do live people visiting a cemetery raise the dead or eventually join the dead? Sickness and death are contagious but health and life are not — except in Jesus.
When Jesus entered this sick, dying world, millions of people caught health and life. The evil effects of sin still spread like the plague, but contagious grace far surpasses it (Rm 5:20). Live with Jesus; eat His body and drink His blood (Jn 6:56); let Him touch you; catch abundant life (Jn 10:10).