Dengue seroprevalence and risk factors for past and recent viral transmission in Venezuela: a comprehensive community-based study.

Dengue transmission in Venezuela has become perennial and a major public health problem. The increase in frequency and magnitude of recent epidemics prompted a comprehensive community-based cross-sectional study of 2,014 individuals in high-incidence neighborhoods of Maracay, Venezuela. We found a high seroprevalence (77.4%), with 10% of people experiencing recent infections. Multivariate logistic regression analysis showed that poverty-related socioeconomic factors (place and duration of residence, crowding, household size, and living in a shack) and factors/constraints related to intradomiciliary potential mosquito breeding sites (storing water and used tires) were linked with a greater risk of acquiring a dengue infection. Our results also suggest that transmission occurs mainly at home. The combination of increasingly crowded living conditions, growing population density, precarious homes, and water storage issues caused by enduring problems in public services in Maracay are the most likely factors that determine the permanent dengue transmission and the failure of vector control programs.

Evolution of dengue virus type 3 genotype III in Venezuela: diversification, rates and population dynamics.

BACKGROUND: Dengue virus (DENV) is a member of the genus Flavivirus of the family Flaviviridae. DENV are comprised of four distinct serotypes (DENV-1 through DENV-4) and each serotype can be divided in different genotypes. Currently, there is a dramatic emergence of DENV-3 genotype III in Latin America. Nevertheless, we still have an incomplete understanding of the evolutionary forces underlying the evolution of this genotype in this region of the world. In order to gain insight into the degree of genetic variability, rates and patterns of evolution of this genotype in Venezuela and the South American region, phylogenetic analysis, based on a large number (n = 119) of envelope gene sequences from DENV-3 genotype III strains isolated in Venezuela from 2001 to 2008, were performed. RESULTS: Phylogenetic analysis revealed an in situ evolution of DENV-3 genotype III following its introduction in the Latin American region, where three different genetic clusters (A to C) can be observed among the DENV-3 genotype III strains circulating in this region. Bayesian coalescent inference analyses revealed an evolutionary rate of 8.48 x 10⁻4 substitutions/site/year (s/s/y) for strains of cluster A, composed entirely of strains isolated in Venezuela. Amino acid substitution at position 329 of domain III of the E protein (A→V) was found in almost all E proteins from Cluster A strains. CONCLUSIONS: A significant evolutionary change between DENV-3 genotype III strains that circulated in the initial years of the introduction in the continent and strains isolated in the Latin American region in recent years was observed. The presence of DENV-3 genotype III strains belonging to different clusters was observed in Venezuela, revealing several introduction events into this country. The evolutionary rate found for Cluster A strains circulating in Venezuela is similar to the others previously established for this genotype in other regions of the world. This suggests a lack of correlation among DENV genotype III substitution rate and ecological pattern of virus spread.

Evaluation of dengue NS1 antigen detection tests with acute sera from patients infected with dengue virus in Venezuela.

The performances of 2 commercial enzyme-linked immunosorbent assay (ELISA) kits (PLATELIA Dengue NS1 AG and Dengue Early ELISA) and a rapid immunochromatography test (Dengue NS1 AG Strip) for detection of dengue NS1 protein were compared using a panel of 87 sera from viremic dengue patients, as well as 36 sera from patients with other acute febrile illnesses. PLATELIA was more sensitive and slightly less specific than Dengue Early ELISA (sensitivity, 71.3% versus 60.9%; specificity, 86.1% versus 94.3%, respectively). The strip test showed an overall sensitivity of 67.8% with a specificity of 94.4%. A lower sensitivity was observed with Dengue Early ELISA for dengue virus (DENV) type 4 (30%) and by the 3 tests for DENV type 2 (56.5%). The use of these kits allows for rapid and specific early diagnosis of dengue infection; however, their sensitivity for each serotype must be further evaluated to guarantee an accurate diagnosis, particularly in those regions where the 4 dengue serotypes are cocirculating.

Nuevas consideraciones en el diagnóstico de rubéola en mujeres embarazadas: un hallazgo de laboratorio / New considerations in the diagnostic rubella in pregnant: an finding of laboratory

El trabajo se realizó con un paciente femenina de 28 años de edad, con ocho semanas de embarazo, quien a solicitud de perfil prenatal obtiene resultados compatibles con infección actual y acude al Instituto Nacional de Higiene "Rafael Rangel" para estudios confirmatorios. Se procesó por duplicado muestras de la paciente sometidas a diferentes condiciones: 1) muestra fresca tomada en el INH "RR" justo antes de su procesamiento, 2) muestra tomada en el INH "RR" almacenada a 40ºC y procesada posteriormente y 3) muestra original proveniente de laboratorio privado. Se usaron tres ELISAS para el diagnóstico de rubéola, dos de captura de anticuerpo para IgM e IgG en las cuales no se trata la muestra y una ELISA de captura de antígeno que incluye absorción de factor reumatoide e inmunocomplejos previo al procesamiento de la muestra. En todas las muestras biológicas del caso los resultados de IgM fueron negativos, exceptuando el de la muestra 1 procesada sin tratamiento donde el resultado fue de IgM positivo. Las IgG resultaron positivas en todas las muestras biológicas del caso, sin registrar variaciones significativas entre ellas. Al eliminar los interferentes (factor reumatoide e inmunocomplejos) se confirma la presencia de un falso positivo de IgM de rubéola en la muestra 1, descartándose infección reciente por rubéola y infección por la misma a los valores obtenidos en la IgG.