Through a cut or an injury where any skin has been broken.
An infection through an animal's bite or sting.(Like the West Nile Virus which spreads though mosquito bite, or Rabies though an infected mammal's bite).
Can be inhaled or consumed and go from the lungs into the other organs causing harm internally.
Kinases. Kinases add phosphate to molecules, and the modification can serve as a "switch" to turn events in the cell on or off. CDKs or cyclin dependent kinases regulate the cell cycle.