To the Editor: Approximately3,000 cases of tickborne encephalitisvirus (TBEV) disease are registeredannually in Europe (1 ). In Italy,indigenous TBEV infection caseshave been only sporadically recordedfrom 1975 through 2001; in addition,serologic investigations in popula-tions at risk in northern Italy haveshown only a low prevalence of spe-cific antibodies (0.6%–5%) (2,3). Asurveillance system for TBEV infec-tions was started after autochthonousTBEV was recognized in late summerand fall 2003 in Friuli-Venezia Giulia(FVG), a small region of northeasternItaly with nearly 1 million inhabitants(4). Surveillance is based on system-atic microbiologic screening of allpatients referred to the emergencydepartments of regional hospitals forsuspected community-acquired cen-tral nervous system infections or feverand headache with a history of tickbite in the past 6 weeks. Screening forTBEV was performed on sera or cere-brospinal fluid (CSF) by enzymeimmunoassay (Enzygnost Anti-TBEvirus Ig, Dade Behring MarburgGmbH, Marburg, Germany) andrepeated on convalescent-phase sera.Demonstration of specific immuno-globulin M (IgM) in serum or CSF inthe acute phase or >4-fold rise inserum antibody titer in the convales-cent phase was interpreted as an indi-cator of recent TBEV infection. Forsurveillance purposes, TBEV infec-tion was defined when hemagglutina-tion inhibition antibody test and neu-tralization assay by a reference labo-ratory confirmed ELISA results (5).Data were collected at a regional ref-erence center, where cases were clas-sified as possible, probable, and con-firmed, according to the new TBEVcase definition (6).
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