According to the Centers for Disease Control and Prevention, shingles (herpes zoster) is only contagious when it is in the blister phase. The danger subsides when crusts develop. Shingles is caused by the same virus that causes chickenpox. The virus can only be spread by direct contact with the blisters.
The disease is not itself contagious, and those coming into contact with the shingles blisters develop chickenpox if they have never had it, says the CDC. The viral disease affects persons who have recovered from chickenpox and mainly older individuals, indicates MedicineNet. There are 1 million cases of shingles in the United States annually.