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We modeled Group A Rotavirus (RVA) and Norovirus genogroup II (GII NoV) transport experiments in standardized (crystal quartz sand and deionized water with adjusted pH and ionic strength) and natural soil matrix-water systems (MWS). On the one hand, in the standardized MWS, Rotavirus and Norovirus showed very similar breakthrough curves (BTCs), showing a removal rate of 2 and 1.7 log10, respectively. From the numerical modeling of the experiment, transport parameters of the same order of magnitude were obtained for both viruses. On the other hand, in the natural MWS, the two viruses show very different BTCs. The Norovirus transport model showed significant changes; BTC showed a removal rate of 4 log10, while Rotavirus showed a removal rate of 2.6 log10 similar to the 2 log10 observed on the standardized MWS. One possible explanation for this differential behavior is the difference in the isoelectric point value of these two viruses and the increase of the ionic strength on the natural MWS.

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RESUMO

Noroviruses (NoVs) are major agents of gastroenteritis outbreaks and hospitalization worldwide. This study evaluated the sensitivity and specificity of the commercially available third-generation RIDASCREEN® Norovirus Enzyme Immunoassay (EIA) kit in comparison to the reverse transcription-polymerase chain reaction (RT-PCR) to detect NoVs in hospitalized children with gastroenteritis. An agreement of 88% (81/92) was observed when comparing EIA with RT-PCR. A sensitivity of 92% and a specificity of 83.3% were demonstrated. Eleven samples were positive by 1 method only (4 RT-PCR/7 EIA). Fourteen samples were sequenced and all classified as NoV genogroup GII-4. The 7 positive only by EIA were also evaluated by electron microscopy, and in 3 (42.9%) samples viral particles with a suggestive morphology of NoVs were visualized. These same samples were tested by seminested-RT-PCR with a positivity of 85.7%. The results obtained in this study demonstrated a significant improvement in the sensitivity and specificity of this updated assay.

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RESUMO

Las gastroenteritis representan una causa importante de morbimortalidad en el mundo y en Venezuela. Su etioligía en infantes es principalmente viral, encontrando a los Norovirus como agentes asociados. Considerando la escasa documentación al respecto, se realizó este estudio para evaluar la prevalencia de Norovirus en niños de 0 a 10 años con diarrea aguda que acudieron a la Policlínica Metropolitana en Caracas; verificando su asociación con otros factores etiológicos y demográficos. 102 muestras fecales fueron sometidas al análisis bacteriológico, parasitológico y viral, utilizando para la detección de Norovirus un ensayo ELISA RIDASCREEN Norwalk-like-Virus. Al análisis estadístico incluyó los índices O. R, y Chi Cuadrado para analizar las frecuencias de los agentes etiológicos, permitiendo además verificar si la diarrea por Norovirus era Independiente de otros patogénos, del sexo y grupos etareos. Se utilizó Excel y el paquete estadístico SPSS 1.0. Los resultados sugirieron que el riesgo de diarrea por Norovirus se sextuplicó en los niños de 1-2 años en comparación con los mayores a 5 años (O.R 5,8842 p:0,0070;x210,879 p:0,012). En los casos positivos, la prevalencia de Norovirus fue del 68,9% y 30% de ellos presentó coinfección con otros patógenos, pero la asociación no fue significativa (p>0,05). Considerando los casos de diarrea que quedan sin diagnósticar, sería lógico pensar que Norovirus circularía con una lata frecuencia en Venezuela, ya que la prevalencia fue superior a la resprtada en otras poblaciones (39,2% vs 5-33%). El impacto de las infecciones por Norovirus en Venezuela se desconece completamente y debe ser estudiado con mayor profundidad.

Gastroenteritis is a very important cause of mobility and mortality in Venezuela and the rest of the World. Their etiology on children is mainly caused by viruses, including Norovirus. Considering the lack of related documentarion in Venezuela, we performed a study in order to calculate the prevalence of Norovirus on children betwen 0 to 10 years old, with acute diarrhea treated on the Policlinica Metropolitna, Caracas; also we analyzed his association with other etiological and demographic factors. 102 stool samples were tested for bacteria parasitic and viruses. For Norovirus we used the ELISA RIDASCREEN Norwalk-like-Virus, (r-biopharm, Germany). The statistical calculations included O.R. and Chi Square ratios, in order to analyze the frequency of the different etiological agents and also to verify if the diarrheas for Norovirus were independent from other pathogenic agents, sex or age groups. We used Excel and SPSS 1.0 software for statistical calculations. The results suggested that the risk of getting a diarrhea caused for Norovirus was 6 times higher on children from 1 to 2 years old than those older that five years old. (OR 5,8842 p:0,0070;x210,879p:0,012) The prevalence for Norovirus was 68,9% and 30% of them presented simultaneous infection with other pathogenic agents, but this association wasn't significative (p>0,05). Considering the high number of diarrhea cases that lack of a proper etiological diagnostic, it's possible that the Norovirus are circulating with a high frequency in Venezuela, due the prevalence reported on this study is above the reported in other population studies (39,2% vs 5-33%). The actual impact of Norovirus in Venezuela is still unknown and must be study with more detail.

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Human caliciviruses were detected by EIA and/or RT-PCR in stool specimens from children with diarrhea treated at out- or in-patient facilities between 1995 and 1998 in Mendoza, Argentina. Mexico virus-like strains detected by primers NV36/51 were transiently prevalent in 1995/1996. Significantly more human caliciviruses were detected when primers were designed from contemporaneously circulating strains. Nucleotide sequences of a highly conserved region in the RNA polymerase gene of 10 selected human caliciviruses were determined. Eight strains were Norwalk-like viruses and two strains were Sapporo-like viruses. Seven of the eight Norwalk-like viruses also were positive by the recombinant Mexico virus antigen EIA. The seven Mexico virus EIA-positive strains revealed two patterns in the RNA polymerase sequences: two strains were closest to Mexico virus and the other five strains were closest to Lordsdale virus. One of the five "Lordsdale" viruses was found to be a naturally occurring recombinant between the Mexico virus and Lordsdale human calicivirus genetic clusters [Jiang et al., (1999b) Archives of Virology 144:2377-2387]. The Mexico virus EIA-negative strain had 73-77% nucleotide identity with the closest related Norwalk-like viruses, indicating it might belong to a new genetic cluster of the Norwalk-like virus genus. The two Sapporo-like viruses were distinct genetically; one belonged to the Houston/90 or Parkville cluster and the other to a new cluster. Some strains appeared to have short periods of prevalence and locally adapted primer pairs significantly increased detection rates. The finding of high diversity of circulating strains, including recombinant strains and strains with previously unrecognized genetic identities, highlights a need for studies of human caliciviruses in these children and other populations.

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