Descriptive Epidemiology of Adult Herpes Zoster (HZ) and Post-Herpetic Neuralgia (PHN) from An Active Surveillance Project, Antelope Valley (AV), California, 2006-2007

Background:
The lifetime risk of HZ is approximately 30% with incidence increasing with age. PHN, persisting pain or discomfort lasting ≥90 days after HZ rash onset, is the most frequently reported complication.

Setting:
Antelope Valley, California (2006-2007)

Population:
Antelope Valley residents ≥50 years of age

Project Description:
Eighty-nine sites reported HZ cases bi-weekly. Verified cases were defined as a unilateral vesicular rash diagnosed by a medical provider. Standardized case reports were completed by phone interview or medical chart abstraction. If cases reported pain at time of interview, calls were made 4 months after rash heal date assessing pain duration. HZ incidence, treatment, presence of pain, and PHN were compared among three age groups.

Results/Lessons Learned:
A total of 881 HZ cases were reported; 261 were excluded due to alternate diagnosis or non-resident status. Of 720 verified HZ cases, 263 (36%) were 50-59 years, 201 (28%) were 60-69 years, and 256 (36%) were ≥70 years. Incidence rates increased with age with 3.1, 4.7, and 6.5 cases per 1,000 population for each respective age group. Fourteen percent of cases reported immunocompromising medical conditions, 49% chronic medical conditions, and 8% reported both. Overall 88% of cases were treated with antiviral therapy, 14% with steroids, 41% with opioids, and 24% with nonprescription medication at initial evaluation. Approximately 90% of cases reported pain, with a median pain score of 8.0 (range: 1-10.0). Pain duration was assessed for 579 cases; 113 (16%) reported ≥90 days of pain. Medication prescribing practices and the proportion of PHN cases did not vary significantly among age groups (P>0.5).
HZ incidence increased with age. Treatment, presence of pain, and the proportion experiencing PHN did not change with advancing age. The considerable PHN reported in persons 50-59 years suggests the need to evaluate ZOSTAVAX vaccine in this age group, currently recommended for those ≥60 years.