Comparing active and passive varicella surveillance in Philadelphia, 2005-2010: recommendations for the transition to nationwide passive varicella disease surveillance.

OBJECTIVE: The Philadelphia Department of Public Health (PDPH) conducts active surveillance for varicella in West Philadelphia. For its approximately 300 active surveillance sites, PDPH mandates biweekly reports of varicella (including zero cases) and performs intensive case investigations. Elsewhere in Philadelphia, surveillance sites passively report varicella cases, and abbreviated investigations are conducted. We used active varicella surveillance program data to inform the transition to nationwide passive varicella surveillance. METHODS: We compared classification of reported cases, varicella disease incidence, and reporting completeness for active and passive surveillance areas for 2005-2010. We assessed reporting completeness using capture-recapture analysis of 2- to 18-year-old cases reported by schools/daycare centers and health-care providers. RESULTS: From 2005 to 2010, PDPH received 3,280 passive and 969 active surveillance varicella case reports. Most passive surveillance reports were classified as probable cases (18% confirmed, 56% probable, and 26% excluded), whereas nearly all of the active surveillance reports were either confirmed or excluded (36% confirmed, 11% probable, and 53% excluded). Overall incidence rates calculated using confirmed/probable cases were similar in the active and passive surveillance areas. Detection of laboratory-confirmed, breakthrough, and moderate-to-severe cases was equivalent for both surveillance areas. CONCLUSIONS: Although active surveillance for varicella results in better classified cases, passive surveillance provides comparable data for monitoring disease trends in breakthrough and moderate-to-severe varicella. To further improve passive surveillance in the two-dose-varicella vaccine era, jurisdictions should consider conducting periodic enhanced surveillance, encouraging laboratory testing, and collecting additional varicella-specific variables for passive surveillance.

Varicela e herpes zóster / Varicella and herpes zoster

O vírus varicela-zóster (VVZ) é um alfa-herpesvírus do gênero varicellovirus cuja característica mais marcante é a capacidade de estabelecer latência em células dos gânglios da raiz dorsal de nervos sensitivos após infecção primária. Compreende a varicela, infecção primária - doença exógena - que é a resposta do indivíduo sem imunidade, e o herpes zóster, doença endógena neurocutânea, que representa imunidade parcial e é causada pela reativação do vírus latente. A varicela é doença benigna, comum da infância, altamente contagiosa, que cursa com febre e erupção generalizada, vesiculosa, acompanhada de muito prurido. O herpes zóster é caracterizado por erupção vesicobolhosa localizada e dolorosa, envolvendo um ou mais dermátomos adjacentes, e causado pela reativação do VVX. Sua principal complicação é a neuragia pós-herpética. A incidência e a gravidade do herpes zóster aumentam com a idade e com o decréscimo da imunidade mediada por células