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Consumption of green vegetable products is commonly viewed as a potential risk factor for infection with enteric viruses. The link between vegetable crops and fecally contaminated irrigation water establishes an environmental scenario that can result in a risk to human health. The aim of this work was to analyze the enteric viral quality in leafy green vegetables from Cordoba (Argentina) and its potential association with viral contamination of irrigation waters. During July–December 2012, vegetables were collected from peri−urban green farms (n = 19) and its corresponding urban river irrigation waters (n = 12). Also, urban sewage samples (n = 6) were collected to analyze the viral variants circulating in the community. Viruses were eluted and concentrated by polyethylene glycol precipitation and then were subject to Reverse Transcription Polymerase Chain Reaction to assess the genome presence of norovirus, rotavirus and human astrovirus. The concentrates were also inoculated in HEp−2 (Human Epidermoid carcinoma strain #2) cells to monitor the occurrence of infective enterovirus. The frequency of detection of the viral groups in sewage, irrigation water and crops was: norovirus 100%, 67% and 58%, rotavirus 100%, 75% and 5%, astrovirus 83%, 75% and 32% and infective enterovirus 50%, 33% and 79%, respectively. A similar profile in sewage, irrigation water and green vegetables was observed for norovirus genogroups (I and II) distribution as well as for rotavirus and astrovirus G−types. These results provide the first data for Argentina pointing out that green leafy vegetables are contaminated with a broad range of enteric viruses and that the irrigation water would be a source of contamination. The presence of viral genomes and infective particles in food that in general suffer minimal treatment before consumption underlines that green crops can act as potential sources of enteric virus transmission. Public intervention in the use of the river waters as irrigation source is needed.

An environmental survey was conducted in order to assess the frequency of detection of picobirnavirus (PBV), human adenovirus (HAdV) and infective enterovirus (iEV) as indicators of faecal contamination in freshwater, and to determine their potential as reporters of the presence of other enteric viruses, such as group A rotavirus (RVA). The study was carried out over a three-year period (2013-2015) in the San Roque Dam, Córdoba, Argentina. The overall frequency detection was 62.9% for PBV, 64.2% for HAdV and 70.4% for iEV. No significant differences were observed in the rates of detection for any of these viruses through the years studied, and a seasonal pattern was not present. Whenever there was RVA detection in the samples analyzed, there was also detection of iEV and/or HAdV and/or PBV. At least one of the viral groups analyzed was demonstrated in the 100% of the samples with faecal coliforms values within the guideline limits. In this setting, especially in those samples which reveal faecal indicator bacteria within the guideline limit, we propose to carry out a pathway, involving PBV, HAdV and iEV detection in order to enhance the evaluation of microbiological quality in freshwater in Argentina. The proposed methodological strategy could report faecal contamination in water, mainly of human origin, and the condition of the matrix to maintain viral viability. In addition, the viral groups selected could report the presence of RV.

Water resources contaminated with wastewater are an important source for the dissemination of enteric viruses with an impact on the health of the population. The aim of the study was to assess the viral contamination of freshwater from a dam in Argentina by using infectious enterovirus detection, viral RNA amplification, and a genetic characterization of five enteric viruses associated with diarrhea and hepatitis. Enterovirus infectivity (iEV) was evaluated by cell culture and direct immunofluorescence. The detection of the viral genome of rotavirus (RV), human astrovirus (HAstV), norovirus (NoV), hepatitis A virus (HAV), and hepatitis E virus (HEV) was performed by reverse transcriptase PCR (RT-PCR). A total of 48 water samples from 4 monitoring points on the body of the dam from January to December 2012 and 66 water samples from 3 tourist beaches on the edge of the dam from October 2013 to October 2015 were collected monthly. During the first period, the overall viral frequency detection was 52.1% for group A RV, 50% for HAstV, 60.4% for NoV, 22.9% for HAV, 2.1% for HEV, and 64.6% for iEV. The overall frequency detection for the second sampling was 18.2% for RV and HAstV, 31.8% for NoV, 7.57% for HEV, and 66.7% for iEV. There was no detection of HAV during this period. The genotypes and genogroups detected through the study correlated with the most common genomic variants associated with human gastrointestinal and hepatitis illnesses. The results obtained could alert the health systems and environmental sanitation to make decisions for viral control and prevention in our environment. Fil: Masachessi, Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Pisano, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Prez, Verónica Emilse. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Martínez, L.C.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Michelena, J. F.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Martinez Wassaf, Maribel Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Católica de Córdoba. Facultad de Ciencias Químicas; Argentina Fil: Giordano, Miguel Oscar. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Isa, Maria Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Pavan, Jorge Victorio. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Welter, Adriana Beatriz. Universidad Católica de Córdoba. Facultad de Ciencias Químicas; Argentina Fil: Nates, Silvia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Ré, Viviana Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina

Rotavirus G1 strains represent the most common genotype that causes diarrhea in humans and has been incorporated into both, monovalent and multivalent, rotavirus licensed vaccines. The aim of this study was to determine the evolution profile of G1 rotaviruses in Cordoba, Argentina, over a 27-year period (1980–2006). Intragenotype diversity, represented by lineages within rotavirus circulating strains, was observed. Phylogenetic analysis of the VP7-gene of G1 rotavirus clinical strains showed the circulation of G1 lineage IV and V strains in the 1980s, and co-circulation of lineage I and II strains in the 1990s and 2000–2006. The distribution of G1 in lineages could be linked to multiple nucleotide substitutions distributed across lineages that did not correlate with the emergence of G1 antigenic variants. Moreover, temporal lineage distribution was not linked to significant changes in G1 prevalence. Therefore, the continuous and dominant circulation of G1 over time could not be related to the emergence of antigenic variants in the community. Continuous rotavirus surveillance is necessary to understand rotavirus evolution and to measure how genetic and antigenic changes might affect the effectiveness of vaccines in the future. J. Med. Virol. 85:363–369, 2013. © 2012 Wiley Periodicals, Inc.

Fecal contamination of water is a worrying problem because it is associated with the transmission of enteric pathogenic microorganisms that can cause many infectious diseases. In this study, an environmental survey was conducted to assess the level of viral contamination by viable enterovirus and rotavirus genome in two recreational rivers (Suquía and Xanaes) of Córdoba, Argentina. Quantitative microbial risk assessment (QMRA) was calculated to estimate the risk of rotavirus infection. Water sampling was carried out during a one-year period, the presence of total and fecal coliforms was determined and water samples were then concentrated for viral determination. Cell culture and indirect immunofluorescence were applied for enterovirus detection and RT-qPCR for rotavirus quantification. Coliform bacteria levels found in Suquía River often far exceeded the guideline limits for recreational waters. The Xanaes exhibited a lower level of bacterial contamination, frequently within the guideline limits. Enterovirus and rotavirus were frequently detected in the monitoring rivers (percentage of positive samples in Suquía: 78.6% enterovirus, 100% rotavirus; in Xanaes: 87.5% enterovirus, 18.7% rotavirus). Rotavirus was detected at a media concentration of 5.7 × 105 genome copies/L (gc/L) in the Suquía and 8.5 × 100 gc/L in the Xanaes. QMRA revealed high risk of rotavirus infection in the Suquía, at sampling points with acceptable and non-acceptable bacteria numbers. The Xanaes showed significantly lower health risk of rotavirus infection but it proved to be a public health hazard. The viral occurrence was not readily explained by the levels of bacteria indicators, thus viral monitoring should be included to determine microbiological water quality. These findings provide the first data of QMRA for recreational waters in Argentina and reveal the need for public awareness of the health implications of the use of the river waters. Fil: Prez, Verónica Emilse. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Gil, Pedro Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Temprana, Carlos Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Cuadrado, P. R.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Martínez, L.C.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Giordano, Miguel Oscar. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Masachessi, Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Isa, Maria Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Ré, Viviana Elizabeth. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Pavan, Jorge Victorio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Nates, Silvia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Barril, Patricia Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina

Summary Background On the basis of the published literature, it is still difficult to draw conclusions as to whether picobirnavirus (PBV) circulation is influenced by host species restriction. Objective To provide data regarding the genetic relatedness between porcine and human PBV strains present in Argentina as a means of defining the host range and epidemiology of these viruses. Methods Fecal specimens ( n = 74) collected from kidney transplant patients ( n = 55) and piglets ( n = 19) were analyzed by RT-PCR using primers designed to amplify the porcine PBV genomic segment 2. Amplified sequences were further examined phylogenetically. Results By RT-PCR amplification 14 of 74 samples rendered amplicons of the expected 282 base pair size (8 detected from humans and 6 from pigs). Eleven amplicons (5 from humans and 6 from pigs) were selected for sequencing and subjected to phylogenetic analysis. The eleven amplicons revealed similarities between human and porcine viral sequences that ranged between 94.7 and 100% in identity. Phylogenetic analysis identified these 11 strains as PBV genogroup I-related strains and showed that they grouped as a single separate clade distinct from other PBV strains detected in humans and porcine from other countries. Conclusions The present study suggests that closely related PBV strains infect both pigs and humans in Argentina and that the epidemiology of PBVs is not species restricted.

A study aimed to further understand the biology of porcine picobirnaviruses (PBV) was conducted between November 2003 and January 2008, on a farm located in the outskirts of Córdoba City, Argentina. PBV prevalence was examined by polyacrylamide gel electrophoresis and silver staining (PAGE S/S) on a total of 265 samples collected from pigs divided into four groups, according to age and physiological status. PBV detection rate was highest in the group of sows sampled within the lactogenic period (38.02%; p0.05), followed by pregnant sows (15.09%), piglets aged 2-5 months of age (18.42%) and adult (or =50 weeks) male pigs (0%). In addition, 103 samples collected in 3 follow-up studies were analyzed by PAGE S/S and reverse transcription followed by PCR (RT-PCR). Two of these studies followed female pigs from weaning up to slaughter and a third one from weaning up to 4 pregnancy periods. The results provide evidence that PBV establishes a persistent infection in the host with periods of silence intermingled with periods of low and high viral excretion. High PBV excretion levels were detected by PAGE S/S and were conditioned by age (primary infection) and host physiological status. Low PBV excretion levels were detected by RT-PCR throughout the entire study period. Sequence analysis of selected amplicons indicated that the virus excreted through the follow-up study was the same. These results suggest that porcine PBV is maintained in nature by transmission from infected asymptomatic individuals to susceptible ones.

To date, human adenoviruses are classified into 53 types (types 1-51 and types 53 and 54), which have been grouped into six species named A through F, and the recently identified type 52 has been proposed as member of a new species, G. Type classification is based on type-specific epitopes within loop 1 (L1) and loop 2 (L2) of the hexon protein, which contain seven hypervariable regions that are responsible for type specificity. In this paper, we present the characterization of an adenovirus strain isolated from a male AIDS patient in Cordoba, Argentina. This strain was found to be a member of species D by genomic Sma I restriction analysis. Sequencing of the L1 and L2 regions of the hexon gene and immunological characterization by virus neutralization revealed this hexon to be unique and distinct from the previously identified hexons of types within species D. A seroepidemiologic study in the human population of Cordoba showed that this strain was not endemic in the local human population.

This study compares the presence of environmental poliovirus in two Argentinean populations using oral poliovirus vaccine (OPV) or inactivated poliovirus vaccine (IPV). From January 2003 to December 2005, Córdoba City used IPV in routine infant immunizations, with the exception of intermittent OPV use in August 2005. Between May 2005 and April 2006, we collected weekly wastewater samples in Córdoba City and the province's three major towns, which continued OPV use at all times. Wastewater samples were processed and analyzed for the presence of poliovirus according to WHO guidelines. During the months of IPV use in Córdoba City, the overall proportion of poliovirus-positive samples was 19%. During an intermittent switch from IPV to OPV, this proportion increased to 100% within 2 months. During the 3 months when IPV was reintroduced to replace OPV, a substantial proportion of samples (25%) remained positive for poliovirus. In the OPV-using sites, on average, 54% of samples were poliovirus positive. Seventy-seven percent of poliovirus isolates showed at least one mutation in the VP1-encoding sequence; the maximum genetic divergence from the Sabin strain was 0.7%. Several isolates showed mutations on attenuation markers in the VP1-encoding sequence. The frequency or type of virus mutation did not differ between periods of IPV and OPV use or by virus serotypes. This study indicates that the sustained transmission of OPV viruses was limited during IPV use in a middle-income country with a temperate climate. The continued importation of poliovirus and genetic instability of vaccine strains even in the absence of sustained circulation suggest that high poliovirus vaccine coverage has to be maintained for all countries until the risk of reintroduction of either wild or vaccine-derived poliovirus is close to zero worldwide.

The molecular characterization of partial- length genomic segment 2 of porcine picobirnavirus (PBV) strains and the development of a specific reverse transcription-PCR (RT-PCR) assay for detection of virus in feces are reported. Phylogenetic analysis indicated that the studied porcine isolates were more closely related (>85% identity) to human PBV belonging to genogroup I than to the other porcine PBV described so far. Analysis by RT-PCR and polyacrylamide gel electrophoresis of fecal samples collected in Venezuela and Argentina showed that PBV circulate at high frequencies in piglets.

Picobirnavirus' (PBV) association with diarrhea in children is not reliably established and the potential role of pathogenic PBV needs further investigations.The aim of this study is to clarify the role of PBV in diarrhea illness in children.Between January 1977 and December 2002, 2224 stool specimens were collected from children3 years old with diarrhea illness. All samples were analyzed by the polyacrylamide gel electrophoresis technique (PAGE) for the presence of bisegmented dsRNA virus genomic pattern. Gels were dried and archived. This study procedure allowed us to keep a laboratory electrophoretic record of each sample assayed. In the present study, all the electrophoretic records were reviewed in order to identify PBV positive samples.Two out of 2224 (0.09%) stools were positive for large genome profile of PBV. These two positive samples were collected from hospitalized children1 year old; one of them presenting rotavirus co-infection.The findings obtained in the present report support strong evidence that large genome profile PBV can be considered more an occasional viral agent rather than an etiological agent associated with diarrheal illness.

A picobirnavirus (PBV) analysis was carried out by polyacrylamide gel electrophoresis of 513 stool samples obtained from 150 animal species collected from the Córdoba city zoo. The purpose of the present study was to determine susceptible species for PBV infection, the viral excretion pattern in infected animals, and the potential association with PBV diarrheic illness. Our findings suggest that PBVs are widespread in animals and could have a similar excretion behavior to that previously detected in infected humans. No disease association with PBV infection could be demonstrated. Thus, infected animals could be persistently infected asymptomatic carriers and could serve as reservoirs of infection.

A total of 258 human sera positive for measles antibodies were divided into four different groups: group 1 contained 54 sera from children after natural measles infection (immunoglobulin M [IgM] positive, early infection phase), group 2 contained 28 sera from children after measles vaccination (IgM positive, early infection phase), group 3 contained 100 sera from healthy adults (natural long-lasting immunity), and group 4 contained 76 sera from healthy children (postvaccinal long-lasting immunity). In the early phase of infection, the percent distributions of measles virus-specific IgG isotypes were similar between natural and postvaccinal immune responses. IgG1 and IgG4 were the dominant isotypes, with mean levels of detection of 100% (natural infection) and 100% (postvaccinal) for IgG1 and 96% (natural infection) and 92% (postvaccinal) for IgG4. In comparison, the IgG4 geometric mean titer (GMT) in the early phase of natural infection was significantly higher than the IgG4 GMT detected in the postvaccinal immune response (80 versus 13; 95% confidence interval). In the memory phase, IgG2 and IgG3 responses decreased significantly in both natural infection and postvaccinal groups, while IgG1 levels were maintained. In contrast, the IgG4 postvaccinal immune response decreased strongly in the memory phase, whereas IgG4 natural long-lasting immunity remained unchanged (9 versus 86%;P< 0.05). The results obtained suggest that IgG4 isotype could be used in the early phase of infection as a quantitative marker and in long-lasting immunity as a qualitative marker to differentiate between natural and postvaccinal immune responses.

In recent years, several types of human adenovirus (HAdV) have arisen from the recombination between two or more previously known HAdV types, but their epidemiology is poorly understood. In this study, we investigated the circulation of HAdV-58, a recently described HAdV isolated from an HIV-positive patient in Córdoba city, Argentina. For this purpose, a 30-month survey was conducted to study the presence of this type of adenovirus in sewage samples collected at the inlet from a wastewater treatment plant in Córdoba city, Argentina. Complementarily, the virus was sought in stools of HIV-positive patients. Although HAdVs were detected in human stool samples and in a high percentage of sewage samples, no evidence of HAdV-58 circulation was detected. We suggest that there is no endemic circulation of HAdV-58 in the geographical local area. The trend is that the number of identified HAdVs increases over time. In this context, understanding the current circulating HAdVs may be biologically relevant. Fil: Ferreyra, L. J.. Universidad Nacional de Cordoba. Facultad de Medicina. Departamento de Medicina. Cat.de Bacteriologia y Virologia Medicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Giordano, M. O.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Martinez, L. C.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Barril, Patricia Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Masachessi, Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Isa, Maria Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Poma, Hugo Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones Para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones Para la Industria Química; Argentina Fil: Rajal, Verónica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones Para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones Para la Industria Química; Argentina Fil: Biganzoli, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Nates, Silvia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Pavan, Jorge Victorio. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina. Universidad Nacional de Cordoba. Facultad de Medicina. Departamento de Medicina. Cat.de Bacteriologia y Virologia Medicas; Argentina

The present work provide data about the maintenance of picobirnavirus (PBV) infection during adulthood in a mammalian host. For this purpose PBV infection was studied in an adult orangutan (Pongo pygmaeus) by PAGE/SS, RT-PCR and nucleotide sequencing. PBV infection in the animal was asymptomatic and was characterized by interspaced silent and high/ low active viral excretion periods. The PBV strains excreted by the studied individual were identified as genogroup I and revealed a nucleotide identity among them of 64-81%. The results obtained allowed to arrive to a deeper understanding of the natural history of PBV infection, which seems to be characterized by new-born, juvenile and adult asymptomatic hosts which persistently excrete closely related strains in their feces. Consequently, picobirnaviruses could be considered frequent inhabitants of the gastrointestinal tract, leaving the question open about the molecular mechanisms governing persistent and asymptomatic coexistence within the host and the potential host suitability to maintain this relationship.

Little is known about long-lasting measles protective immunity when exposure to wild-type or vaccine measles virus precedes HIV infection. The results obtained suggest that measles immunity wanes and the lowest measles geometric mean titres (GMT) were significantly associated with measles vaccine-induced immunity in individuals that later developed HIV infection (86% prevalence, GMT 164 mIU/ml) compared to naturally induced immunity in HIV-infected adults (100% prevalence, GMT 340 mIU/ml, P= 0·0082) or non-HIV infected adults (100%, GMT 724 mIU/ml, P= 0·0001), and vaccine-induced immunity in non-HIV-infected adults (100%, GMT 347 mIU/ml, P= 0·017). The study was conducted in an area without wild-type virus circulation since 2000. The absence of virus circulating may alter the paradigm of lifelong immunity to measles virus after vaccination. As the proportion of HIV-infected individuals possessing only vaccine-induced immunity continues to grow, checking the status of measles immunity in this group is strongly recommended Fil: Isa, Maria Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Universidad Catolica de Córdoba. Facultad de Medicina. Clinica Universitaria Reina Fabiola; Argentina Fil: Pavan, Jorge Victorio. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sicilia Don, Paola Ermelinda. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina Fil: Grutadauria, S.. Sanatorio Allende; Argentina Fil: Martinez, Laura Cecilia. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina Fil: Giordano, Miguel Oscar. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Masachessi, Gisela. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Barril, Patricia Angelica. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Nates, Silvia Viviana. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

To evaluate the prevalence of enteric viruses and their possible association with diarrhea, 244 stool samples were collected from HIV-infected and uninfected patients with or without diarrhea (subgroups I-a, Ib, II-a, and II-b, respectively). Subjects were screened by polyacrylamide gel electrophoresis, latex agglutination, and enzyme immunoassays for rotaviruses, adenoviruses, picobirnaviruses, and astroviruses. Enteric viruses were found significantly more often in specimens from HIV patients (20%) than in specimens from uninfected HIV patients (0%) (p0.05). Picobirnavirus was detected in 14.63% of 82 HIV-infected patients with diarrhea, but it was detected neither in those without diarrhea (0%) (p0.05) nor in the groups of uninfected HIV subjects (0%) (p0.05). Nor could astrovirus (subgroups I-a [4.00%] versus subgroup I-b [5.26%],p0.05) or enteric adenovirus (subgroup I-a [1.22%] versus subgroup I-b [0%], p0.05) be linked to the diarrhea disorder in HIV-infected patients. Rotaviruses were not detected in any of the clinical subgroups studied. Enteric viruses were detected in 15 of 93 (16.13%) of the HIV-infected patients with CD4+ T cell count200/microl and 3 of 19 (15.79%) of those HIV-infected individuals with a CD4+ T cell count 200-499/microl, showing no significant difference (p0.05). According to our data, unusual enteric viruses such as picobirnavirus, astrovirus, and enteric adenovirus occur in HIV-infected population in Córdoba, Argentina. However, only picobirnaviruses could be significantly associated with diarrhea in these patients.

Culture amplification in colon adenocarcinoma cell line (CaCo-2) combined with enzyme immunoassay (Pathfinder ELISA) was developed as a supplementary tool for rotavirus diagnosis. One hundred and thirty stools in which results by polyacrylamide gel electrophoresis (PAGE) were in agreement with those obtained by ELISA were amplified in the CaCo-2 cell line. After the first passage 100% specimens were revealed as positive by ELISA. This result was confirmed by PAGE and direct electron microscopy (EM) which increased the rates of rotavirus detection up to 100% after the third and fifth cell passages, respectively. All of the amplified negative stools were confirmed as negative. Among discordant results, three of the eight specimens positive by ELISA but negative by PAGE were confirmed as true positive after the third cell passage. False positive ELISA results could be discarded when the samples were culture amplified and retested by the same ELISA. Using the CaCo-2 amplification-ELISA as supplementary assay, sensitivity and specificity were 1.000 and 0.953 for ELISA and 0.917 and 1.000 for PAGE, respectively. The combined CaCo-2 cell line amplification-immunoassay method proved to be suitable both to evaluate increase in sensitivity of newly developed rotavirus assays and for rotaviral amplification before antigen assays.

Human rotaviruses (HRV) are the most important etiologic agents of acquired diarrhea in infants and young children worldwide. Therefore, the early diagnosis is essential for effective patient management and infection control. We have developed a rapid, simple technique for the diagnosis of rotavirus based on the sensitive detection of rotavirus double-stranded RNA genome segments separated in vertical agarose gels and developed by silver staining (AGE-SS). This method also has the ability to detect differences in the electrophoretic mobility of RNA bands among group C rotaviruses, reovirus, and group A rotaviruses. The results indicate that this assay is as sensitive and specific as the polyacrylamide gel electrophoresis and silver stain method (PAGE/SS) and it could be applied on large scale for the screening of stool suspected of rotaviral diarrhea. This assay does not need sophisticated equipment and the cost per sample is minimal compared with other available assays.

Enteric viruses monitoring in surface waters requires the concentration of viruses before detection assays. The aim of this study was to evaluate different methods in terms of recovery efficiencies of bacteriophage PP7 of Pseudomonas aeruginosa, measured by real-time PCR, using it as a viral control process in water analysis. Different nucleic acid extraction methods (silica–guanidinium thiocyanate, a commercial kit (Qiagen Viral RNA Kit) and phenol–chloroform with alcohol precipitation) exhibited very low recovery efficiencies (0.08–4.18 %), being the most efficient the commercial kit used for subsequent experiments. To evaluate the efficiency of three concentration methods, PBS (as model for clean water) and water samples from rivers were seeded to reach high (HC, 106 pfu ml−1 ) and low concentrations (LC, 104 pfu ml−1 ) of PP7. Tangential ultrafiltration proved to be more efficient (50.36±12.91, 17.21±9.22 and 12.58±2.35 % for HC in PBS and two river samples, respectively) than adsorption–elution with negatively charged membranes (1.00±1.34, 2.79±2.62 and 0.05±0.08 % for HC in PBS and two river samples, respectively) and polyethylene glycol precipitation (15.95±7.43, 4.01± 1.12 and 3.91±0.54 %, for HC in PBS and two river samples, respectively), being 3.2–50.4 times more efficient than the others for PBS and 2.7–252 times for river samples. Efficiencies also depended on the initial virus concentration and aqueous matrixes composition. In consequence, the incorporation of an internal standard like PP7 along the process is useful as a control of the water concentration procedure, the nucleic acid extraction, the presence of inhibitors and the variability of the recovery among replicas, and for the calculation of the sample limit of detection. Thus, the use of a process control, as presented here, is crucial for the accurate quantification of viral contamination. Fil: Poma, Hugo Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); Argentina; Fil: Rajal, Verónica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); Argentina; University of California at Davis. Fogarty International Center; Estados Unidos de América; Fil: Blanco Fernandez, Maria Dolores. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Barril, Patricia Angelica. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Giordano, Miguel Oscar. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Masachessi, Gisela. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Martinez, Laura Cecilia. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Isa, Maria Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Freire, María Cecilia. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud; Argentina; Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; Argentina; Fil: Riviello López, Gabriela. Ministerio de Defensa. Perfectura Naval Argentina; Argentina; Fil: Cisterna, Daniel Marcelo. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud; Argentina; Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; Argentina; Fil: Nates, Silvia Viviana. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina; Fil: Mbayed, Viviana Andrea. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Norovirus (NoV) contamination was evaluated in five rivers of Argentina between 2005 and 2011. NoV was present in all sampled rivers, with distinct NoV patterns in waters impacted by different-sized communities. In rivers affected by medium-sized populations (Salta and Cordoba cities) only one or two genotypes were present, GII.4 being the main one, with winter seasonality. In contrast, in the much more heavily populated area of Buenos Aires city the prevalent GII.4 was accompanied by several additional genotypes (GII.4, GII.b, GII.2, GII.7, GII.17, GII.e and GII.g) and one ungenotyped GII NoV, with no clear seasonality. GII.4 2006b was the main variant detected (60.9%). Phylogeographic and phylodynamic analyses performed in region D of the VP1 gene showed a most recent common ancestor in 2002 and a substitution rate of 3.7 × 10− 3 substitutions per site per year (HPD95% = 2.3 × 10− 3 − 5.2 × 10− 3) for this variant still involving a significant population size with a slight decrease since 2008. The spatio-temporal diffusion analysis proposed Europe as an intermediate path between the American Continent and the rest of the World for NoV dissemination. Given the importance of NoV as a cause of epidemic gastroenteritis and the likelihood of its environmental transmission, the results of this work should increase public and institutional awareness of the health risk involved in sewage discharges into the environment. Environmental surveillance of enteric viruses could be a very useful tool not only to prevent waterborne outbreaks, but also to describe the epidemiology of the viruses. The detailed analysis of the viral genomes disposed into the environment contributed to the characterization of the dissemination, diversity and seasonality of NoV in its natural host population. In future studies, environmental surveillance and molecular analysis should be complemented with a quantitative viral risk assessment for estimating the disease burden from viruses in the environment.

A study aimed to determine the infection model that picobirnavirus (PBV) established in birds was conducted in a farm of greater rheas in Cordoba, Argentina. Analysis of stools collected during a longitudinal study involving seven birds provided evidence that PBV is acquired very early in life and establishes a persistent infection in the host, which is characterized by intermingled periods of high, low and silent viral activity. Genomic analysis indicated that the rheas excreted virus with nucleotide sequence identity between 90.5–100 % and that more than one PBV strain with different electropherotype profiles could be involve in the infection. This report provides the first evidence of persistent infection of PBV in birds. The natural history of PBV infection has begun to be understood, and it appears that asymptomatic PBV-infected mammals and birds could persistently excrete the virus in stool samples, contributing to wide circulation of the virus in the environment.

Noroviruses (NoVs) are among the most common viral agents that cause gastroenteritis in humans of all ages worldwide. They are excreted in the feces and introduced into environmental waters as raw or treated sewage. In this work, sewage and water samples collected from the Suquia River in the city of Cordoba, Argentina, were evaluated for the presence of NoV. Phylogenetic analysis demonstrated that the main genotype detected was GII.4, belonging to the widely-distributed 2006b variant, followed by strains related to the putative recombinant GII.g virus. Detected NoVs were more phylogenetically related with recent viruses from other countries than with previous local sequences, suggesting a rapid and wide spread of viral strains that prevents a geographically structured phylogeny. A Bayesian coalescent analysis demonstrated that variants isolated in this work have a most recent common ancestor placed in 2007-2008 with estimated substitution rates of 3.7-5.8×10(-3)s/s/y. Environmental samples showed a mixture of both viral types, pointing up to the co-circulation and the risk of mixed infections and recombination. This is the first report on the detection and characterization of NoV in sewage and river water in Argentina.

SUMMARYVaccination coverage and seroprevalence of poliovirus antibodies were assessed in Argentinean children (aged 8–12 and 19–21 months) living in Cordoba City pre-/post-implementation of a DTwP-IPV-Hib vaccination programme, and compared to those of controls from neighbouring populations receiving a full oral poliovirus vaccine schedule. Vaccination coverage was higher in control areas pre-intervention; this increased post-intervention in Cordoba (>90%) but not in control areas. Poliovirus types 1 and 2 seroprotection rates were >97% in all groups pre-/post-intervention. Type 3 seroprotection rates were generally lower, but increased post-intervention in Cordoba becoming significantly higher than control rates. Anti-type 1 and 3 antibody titres increased twofold and sevenfold, respectively, post-intervention, whereas anti-type 2 antibody titres decreased ~40% in the 8–12 months group. All titres increased in the 19–21 months post-intervention group. The introduction of a three-dose primary DTwP-IPV-Hib schedule maintained protection against poliovirus types 1 and 2, and increased protection against type 3, while vaccine coverage in the study area increased.

In previous research, we concluded that measles virus specific IgG4 antibody titer could be used to differentiate between natural [IgG4 GMT 80 (95% CI, 33 to 191)] and vaccinal source of measles infection [IgG4 GMT 13 (95% CI, 7 to 26)]. The aim of this paper is to show that this new serologic marker (IgG4 measles antibody titer) can be applied to help interpret rare but well documented cases of measles Ig M-positive results in vaccinated individuals who, 1-2 months after vaccination, developed rash and fever and therefore do not meet the criteria for post-vaccinal measles infection. Six measles IgM-positive serum samples obtained from measles vaccinated individuals who developed rash/fever 1 to 2 months post-vaccination were studied by Immunofluorescence assay for the quantification of IgG4 measles specific antibody. IgG4 antibody titers from all these samples were between 1:10-1:20, consequently, the IgM positive results from the study cases could be ascribed to post-vaccinal immune response. Thus, measles virus specific IgG4 antibody titer could be used as a serologic marker of post-vaccinal immune response.

The incidence of human rotavirus G types was determined over a 25-year period (1979–2003) by using reverse transcription-PCR (RT-PCR) to examine 519 stool specimens found to be positive for rotavirus by enzyme linked immunosorbent assay (ELISA) or polyacrylamide gel electrophoresis (PAGE). These stool samples were obtained from children under 3 years old who had been treated for acute diarrhea at public hospitals in Cordoba, Argentina. The present study describes the continued circulation of the common human G types G1 (53.8%), G2 (10.2%), G3 (4.4%), and G4 (27%), and also the detection of the unusual types G8 (0.5%) and G9 (4.2%). Genotype G9 was detected during the 1980–1988 and 1997–2003 periods at relatively low rates. Rotavirus G types distribution was independent of age (1–18 months), gender or out-patient or in-patient status. Unexpectedly, 44.6% of mixed infections were detected, involving common and unusual genotypes. Overall, 95.4% of the typed strains belonged to the most prevalent human serotypes (G1–G4) but the detection of G9 infection throughout this study period highlights the importance of this serotype as a human pathogen. J. Med. Virol. 78:1113–1118, 2006. © 2006 Wiley-Liss, Inc.

Objectives: This study was carried out in order to evaluate the efficacy of the recently developed picobirnavirus (PBV) sets of primers and to establish the phylogenetic relationships of Argentine strains with PBV strains isolated in China and the USA. Methods: Thirteen fecal specimens tested as positive for PBV by polyacrylamide gel electrophoresis were analyzed by reverse transcription-polymerase chain reaction assays using primers target to the genomic segments 2 of PBV strains isolated in China and the USA. The amplicons were sequenced and analyzed. Results: Primers derived from the China strain produced amplicons in only 4 of the 13 specimens (30.76%). No sample was revealed as positive with the primers derived from the US strain. DNA sequencing of polymerase chain reaction products differed in nucleic acid and amino acid sequences by 13.9–42.28% and 18.1–51.1%, respectively. Despite this strain diversity, three domains of conserved nucleotide sequences as well as the amino acid motif D-S-D typical of RNA-dependent RNA polymerase gene of double-strand RNA viruses were identified. Comparatively, these conserved regions were also identified in homologous PBV strains from the USA and China. Phylogenetic analysis showed no time or geographic clustering. Conclusions: These findings provide evidence that PBV may represent an emerging heterogeneous group of viruses.

Information concerning the disease burden of viral gastroenteritis has important implications for the use and monitoring the impact of public health policies. The present study, carried out in Córdoba city, Argentina, documents the epidemiology of severe viral diarrhea as well as the burden of viral gastrointestinal disease in the hospital children admission. A total of 133 stools were collected from hospitalized children (Town Childhood Hospital) suffering from acute diarrhea and studied for the presence of Group A rotavirus, astrovirus and adenovirus 40/41 by enzyme-immuno assay, between November 1997 and October 1998. Enteric viruses accounted for 42.1% of the total diarrheal cases analyzed. Group A rotaviruses, astroviruses, adenoviruses 40/41 and mixed infections were found in 35.3, 4.5, 1.5, and 0.8% studied specimens respectively. We estimated that 1 in 27 children in the 0-35 month-old cohort/range would be annually hospitalized for a viral gastroenteritis illness. The major impact on viral diarrhea lies on rotaviral infection, accouting for 84.0% of the viral diarrheal cases analyzed and for approximately one third of severe diarrheas requiring hospital admission in Córdoba City, Argentina. Dados a respeito do impacto das gastrenterites virais têm implicações importantes para o monitoraramento do impacto das políticas de saúde pública. O presente estudo, feito na cidade de Córdoba, Argentina, documenta a epidemiologia da diarréia viral severa como também o impacto que a mesma representa na admissão hospitalar de crianças. Pesquisou-se a presença de Rotavírus grupo A, Astrovírus e Adenovírus 40/41 por ensaio imuno-enzimático em 133 amostras de fezes obtidas durante o período de novembro de 1997 a outubro de 1998, de crianças hospitalizadas por diarréia aguda. Os virus entéricos constituíram 42,1% do total de casos de diarréia analisados. Encontraram-se Rotavírus Grupo A, Astrovírus, Adenovírus 40/41 e infecções mistas em 35,3; 4,5; 1,5 e 0,8% das amostrras estudadas, respectivamente. Observamos que uma de cada 27 crianças entre 0-35 meses de idade seria hospitalizada por ano devido a uma gastrenterite viral. O principal impacto da diarréia viral é representado pela infecção por Rotavírus, correspondendo a 84,0% dos casos analisados e cerca de um terço das diarréias graves que precisam hospitalização em Córdoba, Argentina.

A total of 154 human serum samples (32 acute-phase and 22 convalescent-phase serum samples obtained within a week and between days 8 and 26 after the onset of rash, respectively, and 100 samples drawn from healthy immune adults) were processed by an immunofluorescence assay for the detection of immunoglobulin M (IgM), total immunoglobulin G (IgG), IgG1, IgG2, IgG3, and IgG4 measles virus-specific antibodies. In the acute phase, IgG1 was seen first, followed by IgG2, IgG3, and IgG4 responses, the mean seropositivity of which gradually increased during convalescence, reaching 100% (standard deviation [SD], 84 to 100%), 57% (SD, 34 to 80%), 86% (SD, 66 to 100%), and 86% (SD, 66 to 100%), respectively. IgG2 rose and fell in connection with IgG3 subclass antibodies, showing a rate of detection of IgG2 and/or IgG3 subclass antibodies of 95.5% (range, 100 to 86.5%) in the convalescent phase of infection. The mean percentage of measles IgG2 and IgG3 seropositivity dropped significantly during the memory phase, to 2% (range, 2 to 6%) and 3% (range, 3 to 7%), respectively ( P < 0.05); meanwhile IgG1 and IgG4 subclass responses remained relatively unmodified in samples obtained years after infection (mean 100% [SD, 96 to 100%] and 86% [SD, 79 to 93%], respectively). Results obtained defined two highly different immune isotypic response patterns. One pattern is restrictive to IgG2 and/or IgG3 in the convalescent phase and is kinetically similar to the IgM antibody response, so its detection could be referred to as a recent viral activity. On the other hand, IgG1 and IgG4 were detected in both the convalescent and memory phases of the immune response, but their isolated occurrence without IgG2 and IgG3 could be related to the long-lasting immunity.

Diarrhea due to enteric pathogens is an important complication of advanced HIV infection. Picobirnaviruses are agents recently linked with human enteritis. In total, 197 fecal samples collected from HIV-infected and noninfected patients with and without diarrhea were investigated for the presence of rotavirus and picobirnavirus by polyacrylamide gel electrophoresis. Picobirnavirus was detected in 8.8% of 57 HIV-infected patients with diarrhea, but it was detected in neither those without diarrhea (p.018) nor in the group of subjects uninfected with HIV (p.022). All genomic electropherotypes of picobirnavirus strains had a wide pattern. Picobirnavirus genome segments varied in size between 2.4 and 2.7 and 1.6 and 1.9 kbp for the slow and fast migrating bands, respectively. Rotaviruses were not detected in any of the clinical groups studied. Two methods for the extraction of nucleic acid-phenol/chloroform and guanidinium thiocynate (GTC)/silica-were compared. Detection of picobirnavirus by polyacrylamide gel electrophoresis was 2.5 times more sensitive following guanidinium thiocynate RNA extraction. This investigation offers preliminary results about the circulation of picobirnavirus in HIV-infected patients in Córdoba, Argentina.In 1988, a new group of viruses containing a bisegmented double-stranded RNA genome was described and named "picobirnavirus" (PBV). Viruses with similar properties have subsequently been found in fecal specimens collected from HIV-infected and noninfected patients with gastrointestinal symptoms in several countries. The present study used polyacrylamide gel electrophoresis (PAGE) to examine fecal specimens from 197 HIV infected and noninfected adults, with and without diarrhea, from Cordoba, Argentina, for rotavirus and PBV. PBVs were detected in the stools of 5 HIV-infected patients with diarrhea (8.8%), but in none of the other subgroups (HIV-positive patients without diarrhea, HIV-negative patients with diarrhea, HIV-negative patients without diarrhea). 3 of the 5 stool samples positive for PBV were also positive for intestinal parasites (mixed infection), but these parasites were found with equal frequency in HIV-infected patients without diarrhea. Rotaviruses were not detected in any of the subgroups. PBV genome segments varied in size between 2.4-2.7 and 1.6-1.9 kbp for the slow and fast migrating bands, respectively. PBV detection by the PAGE technique was 2.5 times more sensitive after guanidinium thiocyanate RNA extraction. Further research is required to determine the duration of excretion of PBVs in HIV-infected patients with diarrhea and understand the immune response to infection.

Background. Measles immunization of children at 1 year of age with a single dose of the current vaccine has successfully reduced measles incidence in Argentina. However, the optimal schedule of measles vaccination of young infants would balance the risk of early loss of maternal antibody in the majority of infants with the risk of primary vaccine failure because of passive measles immunity. This study is the first to document a significant association between loss of passive measles antibody and age among infants born in 1995 and 1996 in Cordoba City, Argentina. Methods. This is a seroprevalence study of 340 infants to investigate the duration of transplacentally derived measles antibody, assayed by a neutralization test, during the first 8 months of age in C6rdoba City, Argentina. Results. The proportion with detectable neutralizing measles antibodies decreased from 85% at 1 month of age to 8% at 8 months of age. The simple logistic model with age (in weeks) as the only variable showed that the decline in the proportion of infants with a positive antibody titer was sharpest during the second and fifth months of age (6.6 and 6.8% per week during a 4-week period, respectively). Conclusions. These findings suggest that 80% of infants are susceptible to measles infection for at least 3 months before routine immunization at 12 months of age.

Background : A variable rate of false-positive results may be observed with commercial assays for the detection of rotavirus and adenovirus antigen in stool specimens, depending on the quality of the reagents and the presence of potentially interfering substances in stool samples. Objective : The present report analyse the discrepant results that could be obtained by the commercially available diagnostic tests and that can mask the reliable viral diagnosis. Study design : One fecal sample was collected from a hospitalized child aged 6 months with acute watery diarrhea and dehydration. The fecal specimen was processed the same day for the rotavirus and adenovirus antigen detection. Results : The sample was positive for rotavirus antigen by one-step membrane test based on immunochromatographic assays (ICA) and enzyme immunoassays (EIA) monoclonal test but it was negative by an EIA polyclonal test, polyacrylamide gel electrophoresis (PAGE) and RT-PCR assays. In the other hand, the sample was positive for adenovirus antigen by ICA and EIA adenovirus type 40/41. Finally, the sample showed by PAGE an electrophoretic profile resembled that of reovirus. Conclusion : The use of a wide repertory of diagnosis tests allowed to reach an unusual reovirus–adenovirus type 40/41 dual infection. This case also point out the potential participation of reovirus in the ethiology of the diarrhea illness.