Some diseases can be passed from one person to another easily. Other infectious diseases are harder to get. If a person kisses or touches another person who is infected with the flu, a cold, measles, or a sore throat, he or she may get their disease. They may also give the person their disease if they cough on them. Other medical conditions such as AIDS, herpes, and hepatitis B, are only passed by closer contact. Having sex with an infected person, blood transfusions, or touching their blood or urine can sometimes pass on these conditions or diseases.