Case-control study of the effect of mechanical trauma on the risk of herpes zoster.

Herpes zoster results from reactivation of latent varicella zoster virus infection. Risk of zoster increases with age and with depressed cell mediated immunity, but relatively little is known about other factors. Case reports and case series have indicated that mechanical trauma may be a risk factor. But these studies had no control group, and physical mishaps and surgical trauma are common in older people. We investigated whether trauma is associated with increased risk of zoster using a case-control design.