Herpes Simplex is a viral infection that is found in cold sores and fever blisters and is contagious even when sores are not visible.
Anyone who comes into contact with the virus is at risk for contracting it. It is often passed on to young children by adults. Herpes Simples is most often spread through having sexual contact with someone who already has it. Someone who does not have a strong immune system, especially due to certain types of medication, is more susceptible to it than others.