Sočan et al. BMC Public Health 2010, 10:360 http://www.biomedcentral.com/1471-2458/10/360 R E S E A R C H A R T I C L E Open Access Varicella susceptibility and transmission dynamics in Slovenia Maja Sočan1*, Nataša Berginc2, Jaro Lajovic3 Abstract Background: A cross-sectional, age-stratified study was conducted to determine varicella-zoster seroprevalence and force of infection in Slovenia. Methods: 3689 serum samples were tested for VZV IgG antibodies with an enzyme immunoassay. Semiparametric and parametric modelling were used to estimate the force of infection. Results: Overall, 85.6% of serum samples were seropositive. Age-specific prevalence rose rapidly in preschool children and over 90% of 8 years old tested positive for VZV. However, 2.8% of serum samples among women of childbearing age were seronegative. Semiparametric modelling yielded force of infection estimates of 0.182 (95% CI 0.158-0.206), 0.367 (95% CI 0.285-0.448) and 0.008 (95% CI 0.0-0.032) for age groups 0.5- < 6, 6-11 and ≥12 years, respectively, and 0.175 (95% CI 0.147-0.202), 0.391 (95% CI 0.303-0.480) and 0.025 (95% CI 0.003-0.046) for age groups 0.5- < 5, 5-9 and ≥10 years, respectively. Conclusions: Regardless of the age grouping used, the highest transmission occurred in children in their first years of school. Background Varicella is among the most common vaccine-preventa- ble childhood diseases in countries with a temperate climate. In preschool and school-aged children it is gen- erally considered to be a mild, self-limiting disease [1]. In newborns, immunocompromised patients, adults and pregnant women, however, it can lead to severe compli- cations such as acute cerebellar ataxia, encephalitis and varicella pneumonia [2-4]. Varicella pneumonia is the most common complication in adults, requiring hospita- lisation in approximately one in 4000 varicella cases [1]. Infection of pregnant women, especially in the first three months of gestation, can cause congenital varicella syndrome in the newborn [5,6]. With a clinical attack rate of 65-85% following a household exposure of susceptible individuals, varicella is a highly contagious disease. Varicella-zoster virus, the causative agent of varicella (and herpes zoster), is preva- lent worldwide, but its epidemiological features differ in temperate versus tropical climates. In temperate regions, varicella is largely a childhood disease with a rapid * Correspondence: maja.socan@ivz-rs.si 1Centre for Communicable Diseases, National Institute of Public Health of Republic of Slovenia, Trubarjeva 2, 1000 Ljubljana, Slovenia acquisition of antibodies in the early years of life [7-16], while in the tropics, it mostly occurs in adolescence or adulthood [17,18]. Also, the VZV-specific antibodies seem to appear much earlier in some European countries than in the others - differences which are difficult to explain [16]. Dissimilarities in environmental determinants (e.g. cli- matic factors) and distinctive social structures may affect the seroepidemiology of VZV. The varicella vaccine was developed over thirty years ago. In 1998, the WHO recommended vaccination against varicella as a part of routine vaccination sche- dules in countries where varicella represents an impor- tant public health problem and socio-economic burden [19]. The WHO recommendations have been adopted by some economically developed countries, including USA and Australia that could afford the implementation of a varicella vaccination programme. Most European countries recommend varicella vaccination only for high-risk groups. Universal routine varicella vaccination programmes were instituted in Germany, Greece, certain regions of Spain and Italy, but not elsewhere [20,21]. The reason for not implementing routine varicella vacci- nation programmes might be the lack of recognition of © 2010 Sočan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.