1. When an infected person touches, sneeze or cough on the person that is not infected it can make the person that is not infected to also have that same disease that is why it is good to always use handkerchief or your elbow to cover your mouth anytime you want to sneeze or cough and we should also make sure we wash our hand Regularly
2. Infectious diseases can also be infected from animals, when an infected animal bite or scratch someone that is not infected it can make the person to be sick, and face other consequences as well that is why it is not good to always handle any animal waste anyhow as you can get infected with toxoplasmosis