The main culprit is the varicella-zoster virus, which is the same virus that causes chickenpox.
Infectious Disease Specialist Alexea Gaffney-Adams, M.D., from Stony Brook University Hospital in Stony Brook, New York, explains the various things that could trigger a shingles outbreak.
Shingles is caused by varicella virus. The varicella virus is the virus that we know as chickenpox. What happens is this varicella virus, after we resolve or recover from our chickenpox infection, the virus lives within our nerves and lives in the head of the nerves called a dorsal root ganglia. It can be reactivated for a number of reasons. Sometimes even just aging is a risk factor.