Seroprevalence of varicella-zoster virus infection in children from Cochabamba: tropical or temperate pattern?

OBJECTIVES: To determine the seroprevalence of varicella-zoster viral (VZV) infections in schoolchildren from the Cochabamba region (Bolivia), and its association with socio-demographic variables, socio-economic status and geographical location. METHODS: Seroepidemiological survey (n = 436) on VZV of schoolchildren living in the Cochabamba region of Bolivia in 2010. An ELISA test was used to measure varicella antibodies. Parents or guardians completed a questionnaire regarding socio-demographic information (age, gender, living area, parental educational level, presence of siblings and number of family members in the household), and a blood sample was collected from each child to check for VZV antibodies. A descriptive and bivariate analysis was performed. RESULTS: The global prevalence of VZV was 78.2% (95% CI 74.3-82.1). It was higher in females (82.1%), pre-adolescents (aged 10.1-13 years: 81.4%) and adolescents (aged >13 years: 80.2%), in children with less well-educated parents (81.3% to 81.6%), in warmer municipalities (81.4% to 82.2%), in rural areas (80.0%), in children with siblings (80.1%), those who although the latter association was not statistically significant. CONCLUSIONS: The prevalence of VZV infection in childhood was relatively high for a tropical country, and much closer to that of temperate countries prior to the introduction of varicella vaccine into vaccination programmes.

Measles in Bolivia: A 'honeymoon period'.

BACKGROUND: Although measles is a highly infectious disease, the live measles vaccine provides protection for over 20 years, and immunity may be lifelong. This study assessed measles seroprevalence in schoolchildren in the Cochabamba region of Bolivia. METHODS: A seroepidemiological survey of measles immunity in 5-16-year-old schoolchildren (n=441) living in the Cochabamba region of Bolivia was performed in March and April of 2010. Representative regional samples of school children from 14 schools were obtained. A parent-administered questionnaire collected sociodemographic and socio-economic status, and serum samples were tested for measles antibodies using an enzyme-linked fluorescent antibody test. The measles prevalence and corresponding 95% confidence intervals (CI) were calculated. A descriptive and bivariate analysis was performed using the ANOVA or the Kruskal-Wallis test according to whether the data were distributed normally (Kolmogorov-Smirnov test p-value<0.05) plus the chi-square test or Fisher's exact test as needed. RESULTS: The global seroprevalence of measles was 69.61% (95% CI 65.32-73.90) and was higher in adolescents (84.16%, 95% CI 77.04-91.28) and Spanish speakers (74.74%, 95% CI 68.56-80.92). The seroprevalence did not differ according to socio-economic status, living area, or number of family members in the household. CONCLUSIONS: This study found a high prevalence of measles susceptibility in Bolivian children. Thus, herd immunity may not have been established, and some outbreak could occur. Authorities should redress this situation before endemic measles transmission occurs nationally and regionally, and there is an urgent need to conduct more seroprevalence studies in the region.