Herpes Zoster Reactivation Causes and Risk Factors

Primary Mechanism of Reactivation

The decline in zoster-specific cell-mediated immunity allows the latent virus in sensory ganglia to travel along nerve pathways, causing inflammation and nerve damage that manifests as the characteristic dermatomal rash 1

The lifetime risk of herpes zoster is estimated at 20-30% in the general population, with incidence rates of 7-10 cases per 1,000 person-years after age 50 2

Herpes zoster incidence is approximately 15-fold higher in HIV-infected adults compared to age-matched controls, and can occur at any CD4+ count 3, 1
High-dose corticosteroids (particularly ≥7.5 mg/day prednisolone) increase the risk of herpes zoster reactivation 4, 5
JAK inhibitors (tofacitinib, baricitinib, upadacitinib, filgotinib) increase the risk of herpes zoster reactivation, with incidence rates 3-4 times higher than placebo 4, 5
Biologic DMARDs increase the risk of herpes zoster reactivation, though less frequently than with JAK inhibitors 5

Ultraviolet light exposure, fever, psychological stress and emotional stress, and menstruation may precipitate reactivation 6

Vaccination is the most effective strategy to prevent VZV reactivation, as it boosts specific T-cell production and VZV-specific immunity 2