Heterogeneous susceptibility to rotavirus infection and gastroenteritis in two birth cohort studies: Parameter estimation and epidemiological implications.

Cohort studies, randomized trials, and post-licensure studies have reported reduced natural and vaccine-derived protection against rotavirus gastroenteritis (RVGE) in low- and middle-income countries. While susceptibility of children to rotavirus is known to vary within and between settings, implications for estimation of immune protection are not well understood. We sought to re-estimate naturally-acquired protection against rotavirus infection and RVGE, and to understand how differences in susceptibility among children impacted estimates. We re-analyzed data from studies conducted in Mexico City, Mexico and Vellore, India. Cumulatively, 573 rotavirus-unvaccinated children experienced 1418 rotavirus infections and 371 episodes of RVGE over 17,636 child-months. We developed a model that characterized susceptibility to rotavirus infection and RVGE among children, accounting for aspects of the natural history of rotavirus and differences in transmission rates between settings. We tested whether model-generated susceptibility measurements were associated with demographic and anthropometric factors, and with the severity of RVGE symptoms. We identified greater variation in susceptibility to rotavirus infection and RVGE in Vellore than in Mexico City. In both cohorts, susceptibility to rotavirus infection and RVGE were associated with male sex, lower birth weight, lower maternal education, and having fewer siblings; within Vellore, susceptibility was also associated with lower socioeconomic status. Children who were more susceptible to rotavirus also experienced higher rates of rotavirus-negative diarrhea, and higher risk of moderate-to-severe symptoms when experiencing RVGE. Simulations suggested that discrepant estimates of naturally-acquired immunity against RVGE can be attributed, in part, to between-setting differences in susceptibility of children, but result primarily from the interaction of transmission rates with age-dependent risk for infections to cause RVGE. We found that more children in Vellore than in Mexico City belong to a high-risk group for rotavirus infection and RVGE, and demonstrate that unmeasured individual- and age-dependent susceptibility may influence estimates of naturally-acquired immune protection against RVGE.

Acute norovirus gastroenteritis in children in a highly rotavirus-vaccinated population in Northeast Brazil.

BACKGROUND: Gastroenteritis is one of the most important causes of morbidity and mortality in children and an important etiological agent is norovirus. OBJECTIVE: We describe the occurrence and characteristics of norovirus diarrhoea in children from Sergipe, Northeast-Brazil, over two consecutive periods of three years following rotavirus vaccine introduction. STUDY DESIGN: A cross sectional hospital-based survey conducted from October-2006 to September-2009 and from July-2011 to January-2013. Acute diarrhoea cases had a stool sample collected and tested for norovirus by RT-PCR and positive samples were sequenced. RESULTS: In total 280 (19.6%) of 1432 samples were norovirus positive, including 204 (18.3%) of 1113 samples collected during the first period and 76 (23.9%) of 318 collected during the second period. The proportion of children with norovirus infection increased significantly through the second study period (χ2 for trend=6.7; p=0.009), was more frequent in rotavirus vaccinated and in younger children (p<0.001). Of 280 norovirus-positive specimens, 188 (67.1%) were sequenced. Of these, 12 were genogroup I and 176 genogroup II. The main genotype was GII.4 (149/188, 79.3%), followed by GII.2 (6, 3.2%) and GII.6 (5, 2.6%). CONCLUSION: Norovirus annual detection rates increased over the study period. The detection of norovirus was higher among young children.

Reduction in Rotavirus Disease and Sustained Predominance of G2P[4] Rotavirus Strain following Introduction of Rotavirus Vaccine in Recife, Brazil.

Rotavirus vaccination was introduced in Brazil in March 2006. We describe the distribution of rotavirus genotypes in children with acute gastroenteritis in a hospital in Recife, Brazil, during pre- and post-vaccination periods. There was a 43.8% reduction in the proportion of diarrhea episodes due to rotavirus. Nevertheless, we observed a sustained predominance of G2P[4] as the main genotype identified in the post-vaccination period.

Incidence of rotavirus and circulating genotypes in Northeast Brazil during 7 years of national rotavirus vaccination.

BACKGROUND AND AIMS: Rotavirus causes severe diarrhoea and Brazil introduced the Rotarix G1P[8] vaccine in 2006. We aimed to describe changes in rotavirus incidence and diarrhoea epidemiology before and after vaccine introduction. DESIGN: (i) hospital-based survey of children with diarrhoea (2006-2012); (ii) diarrhea-mortality and hospitalization surveillance (1999-2012). SETTING: (i) Aracaju and (ii) state and national level. RESULTS: 1841 children were enrolled and 231 (12.5%) had rotavirus. Rotavirus was less frequent from January-June than from July-December (9.4% versus 20.9%, p<0.01), but the seasonal variation was less defined after 2009. Very few rotavirus cases (8-3.9%) were detected in 2011, with an increase in 2012 (13-18.5%). In 2006, unvaccinated children were more likely to have rotavirus, but thereafter unvaccinated and vaccinated children had equally low incidence. Older children and those with rotavirus were more likely to have severe diarrhea episodes. The most frequent genotype from 2006 to 2010 was G2P[4]; except in 2009, when most cases were G1P[8]. Very few G2P[4] were detected from 2011 and 50% cases in 2012 were G8P[4]. Diarrhoea-hospitalizations decreased nationally from 89,934 (2003) to 53,705 (2012; 40.3% reduction) and in the state from 1729 to 748 (56.7% reduction). Diarrhoea-deaths decreased nationally from 4368 in 1999 to 697 in 2012 (84% reduction, p<0.001) and in the state from 132 to 18 (86% reduction). These changes were much larger after vaccine introduction. CONCLUSIONS: The vaccine was associated with substantial reductions in rotavirus incidence and diarrhoea-hospitalizations and deaths. The G2P[4] genotype predominance disappeared over time and may be replaced by other heterotypic genotypes.

Acute diarrhoea in a community cohort of children who received an oral rotavirus vaccine in Northeast Brazil.

Rotavirus is an important cause of childhood diarrhoea. A monovalent rotavirus vaccine (Rotarix®) was introduced into the Immunization Program of Brazil in 2006. In this study, we describe the incidence and burden of disease of rotavirus diarrhoea in two cohorts of children (vaccinated and unvaccinated). We followed two groups of 250 children under one year old, who were enrolled in December 2006 from a low-income residential area in Northeast Brazil. The children were monitored every two weeks for two years. Stool samples from children with diarrhoea were examined for the presence of rotavirus. Rotaviruses were genotyped using real time-polymerase chain reaction. The mean numbers of all-cause diarrhoea episodes/child (adjusted for age) in the first year were 0.87 and 0.84, in vaccinated and unvaccinated children, respectively. During the second year, the number of episodes/child decreased to 0.52 and 0.42. Only 16 (4.9%) of 330 stool samples were rotavirus-positive (10 vaccinated and 6 unvaccinated children) and only P[4]G2 rotaviruses were identified. All-cause diarrhoea episodes were more severe in unvaccinated children in the first year of age (p < 0.05), while vaccinated children had more severe episodes 18 months after vaccination. Rotavirus diarrhoea incidence was very low in both groups.

Acute diarrhoea in a community cohort of children who received an oral rotavirus vaccine in Northeast Brazil

Rotavirus is an important cause of childhood diarrhoea. A monovalent rotavirus vaccine (Rotarix®) was introduced into the Immunization Program of Brazil in 2006. In this study, we describe the incidence and burden of disease of rotavirus diarrhoea in two cohorts of children (vaccinated and unvaccinated). We followed two groups of 250 children under one year old, who were enrolled in December 2006 from a low-income residential area in Northeast Brazil. The children were monitored every two weeks for two years. Stool samples from children with diarrhoea were examined for the presence of rotavirus. Rotaviruses were genotyped using real time-polymerase chain reaction. The mean numbers of all-cause diarrhoea episodes/child (adjusted for age) in the first year were 0.87 and 0.84, in vaccinated and unvaccinated children, respectively. During the second year, the number of episodes/child decreased to 0.52 and 0.42. Only 16 (4.9 percent) of 330 stool samples were rotavirus-positive (10 vaccinated and 6 unvaccinated children) and only P[4]G2 rotaviruses were identified. All-cause diarrhoea episodes were more severe in unvaccinated children in the first year of age (p < 0.05), while vaccinated children had more severe episodes 18 months after vaccination. Rotavirus diarrhoea incidence was very low in both groups.

An evaluation of the RIDASCREEN and IDEIA enzyme immunoassays and the RIDAQUICK immunochromatographic test for the detection of norovirus in faecal specimens.

BACKGROUND: The detection of norovirus by ELISA and immunochromatographic methods may facilitate epidemiological studies into the global disease burden associated with norovirus gastroenteritis and provide a quick method of testing for norovirus infection. OBJECTIVES: To evaluate the new RIDASCREEN norovirus ELISA (3rd generation) and RIDAQUICK norovirus immunochromatographic test on a collection of samples from Brazilian children with acute gastroenteritis, and compare them against the established 2nd generation IDEIA norovirus assay. STUDY DESIGN: Reverse transcriptase PCR, the study reference standard, was used to test 726 specimens for the presence of norovirus. All 96 norovirus positive samples and a systematic selection of negative samples were tested by RIDASCREEN, RIDAQUICK and IDEIA norovirus tests. RESULTS: The sensitivity of RIDASCREEN for the detection of norovirus was 63% (95% CI: 53-72%) and RIDAQUICK 69% (95% CI: 58-78%); both were >98% specific. The IDEIA had a sensitivity of 45% (95% CI: 35-55%), significantly lower than RIDASCREEN and RIDAQUICK (p≤0.01). The sensitivity of RIDASCREEN and RIDAQUICK in detecting GII.4 noroviruses, the principal norovirus strain identified in community and nosocomial infection globally, was 78% and 88% respectively. CONCLUSION: The norovirus RIDASCREEN test may be useful in epidemiological studies of norovirus infection and the norovirus RIDAQUICK test offers an accurate and rapid method of detecting norovirus infection.

Effectiveness of monovalent rotavirus vaccine (Rotarix) against severe diarrhea caused by serotypically unrelated G2P[4] strains in Brazil.

BACKGROUND. In a Latin American trial, a monovalent G1P[8] rotavirus vaccine showed high efficacy against severe rotavirus diarrhea. Protection was lower against serotypically unrelated G2P[4] strains, which circulated infrequently. This case-control study was undertaken to assess the effectiveness of this monovalent G1P[8] rotavirus vaccine against G2P[4] strains in Brazil. METHODS. Case patients were children with severe G2P[4] rotavirus diarrhea who presented at a hospital in Recife, Brazil, from March 2006 through September 2008. Vaccination rates among case patients were compared with rates among 2 groups of control participants-children with rotavirus-negative diarrhea and children admitted for acute respiratory tract infection (ARI)-to calculate vaccine effectiveness, after controlling for the birth month and year. RESULTS. We enrolled 70 G2P[4] rotavirus-positive case patients with severe diarrhea, 484 rotavirus-negative control participants with diarrhea, and 416 control participants with ARI, aged 6 months. Among children aged 6-11 months, the effectiveness of the vaccine against G2P[4] diarrhea was 77% (95% confidence interval [CI], 42%-91%) and 77% (95% CI, 43%-90%) among the rotavirus-negative control participants with diarrhea and control participants with ARI, respectively. Vaccine effectiveness in children aged 12 months decreased to -24% (95% CI, -190% to 47%) and 15% (95% CI, -101 to 64) among the rotavirus-negative control groups with diarrhea and ARI, respectively. CONCLUSIONS. This monovalent G1P[8] rotavirus vaccine was effective against severe G2P[4] rotavirus diarrhea among children aged 6-11 months. Effectiveness declined among children aged 12 months, which suggests waning immunity.

Rotavirus genotypes circulating in Brazil before national rotavirus vaccination: a review.

BACKGROUND: Rotavirus vaccine was recently introduced in Brazil, which has the potential to greatly reduce childhood deaths from diarrhoea. To provide baseline data to assess the effect of mass rotavirus vaccination on the ecology of circulating rotavirus strains, we systematically analysed published studies in the pre-vaccine era. AIMS: To describe the distribution of rotavirus genotypes in Brazil prior to vaccine introduction. METHODS: Systematic literature searches in health-related databases from 1986 to 2006. Information extracted and analysed by time and region. RESULTS: 117 studies with 48,401 participants were included. Of these, 3036 were infected with rotavirus. More than 51 genotype combinations were reported, the distribution of which changed over time. P[8]G1 (43%) was the most frequent genotype throughout, followed by P[8]G9 (22%) and P[4]G2 (7%). The detection rate of P[8]G9 increased, while P[4]G2 decreased during the study period. There was a high frequency of G/P combinations between 1995 and 2000 and a low frequency before and after these years. CONCLUSIONS: While considerable diversity of rotavirus strains was recognized during the pre-vaccine era, three strains comprised 72% of the total analysed. These data provide a baseline against which any changes in circulating rotavirus strains post-vaccine introduction can be measured.

Anticipating rotavirus vaccines in Brazil: detection and molecular characterization of emerging rotavirus serotypes G8 and G9 among children with diarrhoea in Recife, Brazil.

In 2006, Brazil will initiate universal immunization of its 4-million infants with a live attenuated serotype G1P[8] human rotavirus vaccine. In anticipation of the national immunization program, this study was undertaken to characterize rotavirus strains circulating among children in Recife, one of the largest cities in the northeast region of Brazil. Group A rotaviruses were detected in 102 (35%) of 290 faecal specimens collected from children under 5 years of age who presented with acute diarrhoea during a 1-year period between May 2004 and April 2005. In addition to the globally common G1P[8] serotype that accounted for 49% of strains, emerging rotavirus serotypes G8P[6] and G9P[8] represented 2% and 29% of strains, respectively. Following cell culture adaptation, RNA-RNA hybridization demonstrated that two Brazilian G8P[6] rotavirus strains shared a high level of genomic RNA homology with Malawian G8P[6] strains, and a Brazilian G9P[8] strain was related most closely to a G9P[8] strain from India. The results suggest that certain rotavirus strains have a much wider global circulation than generally appreciated. Continued global spread of such strains might challenge the efficacy of current rotavirus vaccines.

Molecular analysis of the 18S rRNA gene of Cryptosporidium parasites from patients with or without human immunodeficiency virus infections living in Kenya, Malawi, Brazil, the United Kingdom, and Vietnam.

An 840-bp fragment of the 18S rRNA gene was used to identify Cryptosporidium spp. recovered from human immunodeficiency virus (HIV)-infected and -uninfected patients from Kenya, Malawi, Brazil, the United Kingdom, and Vietnam. Initial identification was by Ziehl-Neelsen acid-fast staining. Confirmation was by nested PCR, targeting the most polymorphic region of the 18S rRNA gene. Genotyping was by restriction endonuclease digestion of the PCR product followed by nucleotide sequencing. Among 63 isolates analyzed, four genotypes of Cryptosporidium were identified; 75% of the isolates were of the C. parvum human genotype, while the potentially zoonotic species were of the C. parvum bovine genotype (21.7%), the C. meleagridis genotype (1.6% [one isolate]), and the C. muris genotype (1.6% [one case]). HIV-infected individuals were more likely to have zoonotic genotypes than the HIV-uninfected individuals. Among the C. parvum group, strains clustered distinctly into either human or bovine genotypes regardless of the geographical origin, age, or HIV status of the patients. The intragenotypic variation observed in the C. parvum human genotype was extensive compared to that within the C. parvum bovine genotype group. The variation within genotypes was conserved in all geographical regions regardless of the patients' HIV status. The extensive diversity within genotypes at the 18S rRNA gene locus may limit its application to phylogenetic analyses.