Noroviruses associated with outbreaks of acute gastroenteritis in the State of Rio Grande do Sul, Brazil, 2004-2011.

BACKGROUND: Acute gastroenteritis norovirus (NoV) in a country of continental dimensions like Brazil has resulted in under-reporting of the number of outbreaks, as well as the genotypes associated. OBJECTIVES: To demonstrate the role of NoV in outbreaks occurring in the State of Rio Grande do Sul, Southern Brazil, we determined its prevalence, as well as the genotypes associated, and evaluated clinical and epidemiological aspects. STUDY DESIGN: NoV investigation was carried out in rotavirus group A negative stool samples from 2265 patients from 741 outbreaks that occurred in the State of Rio Grande do Sul, Brazil, during a period of eight years (2004-2011). NoV detection and nucleotide sequencing for genotype characterization was carried by using sets of primers targeting a conservative Rd-Rp polymerase genome region and the viral capsid gene, respectively. RESULTS: NoVs were detected in 817 stool samples (36.1%) and associated with 327 outbreaks (44.1%). NoV GII.2, GII.3, GII.4, GII.6, GII.12, GII.13, GII.14, GII.15, GII.17, GII.21; and GI.1 and GI.3 were characterized. GII.4 was the most frequently detected (72.3%), with five variants identified (Asia_2003, Hunter_2004, Yerseke_2006a, Den_Haag_2006b, New Orleans_2009). This study describes the first detection of GI.1 and GII.13 and GII.15 in Brazil and demonstrates NoV winter-spring seasonality in this region of the country. CONCLUSIONS: NoVs were responsible for almost 50% of outbreaks, with about 70% of them resulting from genotype GII.4 and its variants. The seasonality observed could help health authorities to establish a system of active surveillance in order to reduce NoV impact especially in congregate settings.

Quantitative and molecular analysis of noroviruses RNA in blood from children hospitalized for acute gastroenteritis in Belém, Brazil.

BACKGROUND: Noroviruses (NoVs) are a common cause of acute gastroenteritis (AGE) and until now, little is known about its ability to spread outside the gut. OBJECTIVES: We aim to investigate the role of NoVs causing viremia in children hospitalized for AGE, as well as to correlate the presence of NoVs RNA in serum with clinical severity and stool viral load. STUDY DESIGN: Paired stool and serum samples were collected from 85 pediatric patients under 6 years hospitalized for AGE from March to September 2012 in Belém, Brazil. Enzyme-linked immunosorbent assay (EIA) and reverse transcription quantitative PCR (RT-qPCR) were used to detect and quantify NoVs, respectively. Phylogenetic analysis of the partial ORF2 region was used to genotype the strains detected. RESULTS: NoVs were detected in 34.1% (29/85) of stool samples. By qRT-PCR, we found a high rate of NoVs' RNA in serum samples (34.5%) among NoVs-positive AGE cases, and was associated with a longer hospitalization (6.5 vs. 4.0 days; p=0.006), as well as with a higher stool viral load (3.9×10(11) vs. 1.1×10(11) GC/g; p=0.0472). NoVs strains were classified as GII.4 (90% of genotyped strains) and GII.7 (10%). The same genotype was found in paired stool and serum samples. CONCLUSION: Detection and molecular characterization of NoVs GII in paired stool and serum samples suggest that the dissemination of NoVs to the blood stream is not uncommon, but the role of viruses spread outside the gut and the relationship with disease severity need to be further addressed.

Characterization of norovirus-associated traveler's diarrhea.

BACKGROUND: Traveler's diarrhea is the most common medical complaint of international visitors to developing regions. Previous findings suggested that noroviruses (NoVs) are an underappreciated cause of traveler's diarrhea. METHODS. In the present study, we sought to define the presence of NoVs in 320 acute diarrheic stool samples collected from 299 US students who traveled to Guadalajara, Cuernavaca, or Puerto Vallarta, Mexico, during the period from 2007 through 2008. Conventional and quantitative real-time polymerase chain reaction assays were used to detect and determine NoV loads in stool samples. NoV strains were characterized by purification of viral RNA followed by sequencing of the viral capsid protein 1 gene. Sequences were compared using multiple sequence alignment, and phylogenetic trees were generated to evaluate the evolutionary relatedness of the viral strains associated with cases of traveler's diarrhea. RESULTS: NoV RNA was detected in 30 (9.4%) of 320 samples. Twelve strains belonged to genogroup I, and 18 strains belonged to genogroup II. NoV prevalence was higher in the winter season than in the summer season (23% vs 7%, respectively; P = .001). The cDNA viral loads of genogroup I viruses were found to be 500-fold higher than those of genogroup II strains. Phylogenetic analysis revealed a diverse population of NoV strains over different locations and years. CONCLUSIONS: NoV strains are important causes of traveler's diarrhea in Mexico, especially during the wintertime, and US students in Mexico may represent a suitable group for future NoV vaccine efficacy trials.

Prospective characterization of norovirus compared with rotavirus acute diarrhea episodes in chilean children.

BACKGROUND: Rotavirus and more recently noroviruses are recognized as main causes of moderate to severe acute diarrhea episodes (ADE) in children < or =5 years of age. Comparing epidemiologic and clinical features of norovirus to rotavirus ADE will aid in the decision-making process required to develop norovirus vaccines. METHODS: Surveillance for ADE occurring in children < or =5 years of age was implemented in the emergency department (ED) and ward of a large hospital in Santiago and Valparaiso, and in 4 outpatient clinics in Santiago. A stool sample was obtained within 48 hours of consultation for rotavirus detection by enzyme-linked immunosorbent assay and noroviruses by enzyme-linked immunosorbent assay or reverse transcription polymerase chain reaction. For ED and hospital rotavirus and norovirus ADE parents were instructed to monitor clinical findings associated with severity until the end of the episode. The 20-point Vesikari score was used to determine disease severity. RESULTS: Between July 2006 and October 2008 rotavirus and noroviruses were detected in 331 (26%) and 224 (18%) of 1913 ADE evaluated. The proportion of rotavirus-positive samples in hospital ward, ED, and outpatient clinic was 40%, 26% to 30%, and 13% compared with 18%, 17% to 19%, and 14% for noroviruses. Mean age and 25%-75% interquartile interval of children with rotavirus and norovirus ADE were remarkably similar, 15.6 months (9-20), and 15.5 months (9-19), respectively. Rotavirus cases displayed an autumn-winter peak followed 2 to 3 months later by the norovirus peak. The mean (interquartile) for the Vesikari score was 12.9 (11-15) and 11.9 (9-14.5) for rotavirus (N = 331) and norovirus (N = 224) ADE, respectively, P = 0.003. Compared with norovirus, rotavirus ADE were more common in the 11 to 16 severity score interval (P = 0.006), had a higher maximum stool output in a given day (P = 0.01) and more frequent fever (P < 0.0001). Duration of diarrhea, presence, duration and intensity of vomiting, and intensity of fever did not differ between viruses. Mixed rotavirus and norovirus infections were uncommon (<1%) and not clinically more severe. Clinical severity of ADE in young infants was similar for rotavirus and lower (P = 0.03) for noroviruses compared with older children. CONCLUSION: Noroviruses are a significant cause of moderate to severe endemic ADE in Chilean children. Although significantly less severe than rotavirus as a group, most norovirus episodes were moderate to severe clinically. An effective norovirus vaccine would be of significant additional benefit to the current rotavirus vaccine in decreasing disease burden associated with ADE.

Surveillance of norovirus infections in the state of Rio De Janeiro, Brazil 2005-2008.

A 4-year (2005-2008) norovirus (NoV) surveillance study was conducted in the state of Rio Janeiro, Brazil, to demonstrate the role of these viruses in outbreaks and sporadic cases of acute gastroenteritis. A cohort of 1,687 fecal samples was obtained from patients with gastroenteritis; 324 were rotavirus-positive. Of the remainder 1,363 rotavirus-negative samples, 1,087 samples were tested for NoV RNA in this study. The study enrolled 267 outpatients from Municipal Public Health Centers and 820 inpatients, whose samples were obtained by active surveillance in Public Hospitals. Fecal samples were tested by reverse transcription (RT) followed by polymerase chain reaction (PCR) using the MON 431-434 set of degenerate primers for NoV GI and GII detection, and there were 35.1% (381/1,087) positive samples for NoV, consisting of 30.2% (248/820) and 49.8% (133/267) from inpatient and outpatient, respectively. Children infected by NoV had significantly more frequent mucus in feces, vomiting and fever. No seasonal pattern in NoV infections was observed in patients admitted to hospital; however, two peaks of NoV infections were observed from ambulatory cases, suggesting that there was an occurrence of outbreaks in those time periods. Molecular characterization revealed GII to be the most prevalent genogroup, totaling 96.3% (104/108) of all sequences analyzed, and GII.4 was the genotype detected most frequently (80.7%), followed by GII.6, 3, 14, 7, and 8. Two GI strains, GI.2 and GI.3, were also observed. The number of outbreaks and sporadic cases described in this study highlights the need to implement diagnosis of NoV in surveillance laboratories.

Symptomatic and asymptomatic rotavirus and norovirus infections during infancy in a Chilean birth cohort.

BACKGROUND: Rotavirus and more recently norovirus have been recognized as 2 of the most common causes of acute diarrhea in children. Comparative analysis of these infections in a birth cohort has not been performed and can provide relevant insight on clinical and viral behaviors. METHODS: Mother-infant pairs from middle-low socioeconomic background living in the Metropolitan Region of Chile are being followed for 18 months in 2 outpatient clinics. Infants are evaluated monthly for asymptomatic excretion of rotavirus and norovirus and during acute diarrhea episodes (ADE) for rotavirus, norovirus, and bacterial enteropathogens. Severity of ADE is evaluated using the Vesikari score. RESULTS: Between July 1, 2006 and September 1, 2008 a total of 198 children were followed for a mean of 15.7 months. Asymptomatic rotavirus and norovirus infections were detected in 1.3% and 8% of 2278 stool samples compromising 14% and 57% of infants, respectively. Incidence of ADE was approximately 0.8 for the first year of life and approximately 0.6 for the 13 to 18 month age group. Rotavirus and norovirus were detected in 15% and 18% of 145 ADE evaluated. Mean Vesikari score was 10.4 and 7.4 for rotavirus and norovirus respectively (P = 0.01) and severity was not associated with age of patients for either virus. Reinfections were more common for norovirus asymptomatic episodes: 44% versus 19% (P = 0.01) and borderline for symptomatic episodes: 40% versus 11% (P = 0.08). Rotavirus genotype G9P8 and norovirus genogroup II (GII) predominated although most asymptomatic episodes for both viruses were nontypable. None of 19 symptomatic GII norovirus infections had a previous documented GII infection compared with 10 of 31 asymptomatic GII infections (OR = 0. 95% CL = 0, 0.59; P = 0.008). CONCLUSIONS: Children had suffered a mean of approximately 1.4 ADE by 18 months of age of which 15% and 18% were caused by rotavirus and norovirus, respectively. In general rotavirus infections were more severe than norovirus infections and for both viruses severity was not related to age. Norovirus reinfections were significantly more common than rotavirus reinfections but for GII norovirus a primary infection seems to confer protection against clinically significant reinfections.

[Sudden death of a child due to aspiration of the gastric content during an infection with Norwalk-like virus]. / Muerte repentina de un niño por aspiración del contenido gástrico durante una infección con el virus de Norwalk-like.

The death of a 1.5-year-old child due to bronchoaspiration of the gastric content in the development of a letal infection caused by Norwalk-like virus was reported. The viral gastrointestinal diseases are common but they rarely produce a severe disease. Recent investigations show that Norwall-like virus (Noro-Virus) is the most frequent gastrointestinal pathogen in Central Europe. The etiological diagnosis of the gastrointestinal disease, starting from autopsy material, was only possible by polymerase chain reaction. The introduction of this technique allowed to reduce the number of cases of gastrointestinal diseases without etiological diagnosis and, at the same time, to increase the demonstration of the occurrence of infection caused by Norwalk-like virus.

Seroprevalence and seroincidence of Norwalk-like virus infection among Brazilian infants and children.

To determine the importance of Norwalk-like viruses (NLVs) as pediatric pathogens in a developing country, the seroprevalence and seroincidence of this group of viruses in a cohort of children less than 4 years of age in an urban shantytown in northeastern Brazil was examined. Serum samples were collected approximately every 6 months from 135 children who were surveyed three times each week for diarrhea and vomiting. NLV IgG was measured by an enzyme immunosorbent assay (EIA) with recombinant Norwalk virus capsid protein. Overall NLV seroprevalence was 71%, and the overall NLV seroconversion rate was 0.7 seroconversions per child-year. The highest age-specific NLV seroconversion rate (0.8 seroconversions per child-year) was observed in the 13-24-month age group. For all study children, the incidence of diarrhea and vomiting was significantly greater (P < 0.01) during time periods spanned by serum pairs that indicated NLV seroconversion compared with time periods without NLV seroconversion. However, NLV seroconversion was not associated with gastrointestinal symptoms during the first year of life.