The second wave of COVID-19 occurred in South America in early 2021 and was mainly driven by Gamma and Lambda variants. In this study, we aimed to describe the emergence and local genomic diversity of the SARS-CoV-2 Lambda variant in Argentina, from its initial entry into the country until its detection ceased. Molecular surveillance was conducted on 9356 samples from Argentina between October 2020 and April 2022, and sequencing, phylogenetic, and phylogeographic analyses were performed. Our findings revealed that the Lambda variant was first detected in Argentina in January 2021 and steadily increased in frequency until it peaked in April 2021, with continued detection throughout the year. Phylodynamic analyses showed that at least 18 introductions of the Lambda variant into the country occurred, with nine of them having evidence of onward local transmission. The spatial–-temporal reconstruction showed that Argentine clades were associated with Lambda sequences from Latin America and suggested an initial diversification in the Metropolitan Area of Buenos Aires before spreading to other regions in Argentina. Genetic analyses of genome sequences allowed us to describe the mutational patterns of the Argentine Lambda sequences and detect the emergence of rare mutations in an immunocompromised patient. Our study highlights the importance of genomic surveillance in identifying the introduction and geographical distribution of the SARS-CoV-2 Lambda variant, as well as in monitoring the emergence of mutations that could be involved in the evolutionary leaps that characterize variants of concern.

Environmental surveillance of water sources is important to monitoring viral hepatitis transmission in clinical settings. This study investigated the circulation of hepatitis A (HAV) and E (HEV) viruses in sewage and clinical samples from Argentina. Between 2016 and 2017, 80 raw sewage samples and 86 clinical samples (stool and serum) from suspected cases of hepatitis A and hepatitis E were obtained. HAV and HEV were tested by both real-time and nested PCR. Positive samples were sequenced for genotype determination and phylogenetic analysis. Overall, HAV was recovered in 39% of sewage samples and 61.1% of clinical samples. HEV was detected in 22.5% of sewage samples and 15.9% of clinical samples. HAV was found more frequently in sewage during the winter and in clinical samples in spring; HEV was more prevalent in sewage during summer and in clinical samples in autumn. All HAV isolates belonged to genotype IA and HEV isolates belonged to genotype 3, the most prevalent genotypes in South America. High prevalence of HAV and HEV in environmental and clinical samples in Mendoza, Argentina was observed. These findings reinforce the importance of environmental surveillance and implementation of health strategies to control the spread of HAV and HEV in developing countries.

The COVID-19 pandemic has lately been driven by Omicron. This work aimed to study the dynamics of SARS-CoV-2 Omicron lineages during the third and fourth waves of COVID-19 in Argentina. Molecular surveillance was performed on 3431 samples from Argentina, between EW44/2021 and EW31/2022. Sequencing, phylogenetic and phylodynamic analyses were performed. A differential dynamic between the Omicron waves was found. The third wave was associated with lineage BA.1, characterized by a high number of cases, very fast displacement of Delta, doubling times of 3.3 days and a low level of lineage diversity and clustering. In contrast, the fourth wave was longer but associated with a lower number of cases, initially caused by BA.2, and later by BA.4/BA.5, with doubling times of about 10 days. Several BA.2 and BA.4/BA.5 sublineages and introductions were detected, although very few clusters with a constrained geographical distribution were observed, suggesting limited transmission chains. The differential dynamic could be due to waning immunity and an increase in population gatherings in the BA.1 wave, and a boosted population (for vaccination or recent prior immunity for BA.1 infection) in the wave caused by BA2/BA.4/BA.5, which may have limited the establishment of the new lineages.

Introduction and Objectives: Accessing to a closed population such as prisoners opens a great possibility for controlling HCV infection through treatment with Direct-acting antivirals (DAAs). Introduction. This study aimed to determine HIV, syphilis, HBV and HCV prevalence in the eight penal institution inmates of Mendoza´s province to achieve microelimination of viral hepatitis. Materials and Methods: During 2019, HIV, HCV, syphilis and HBsAg tests were offered to all inmates. In order to characterize risk factors associated with this population, they were given a voluntary self-administered survey on sexual practices, drug use and self-perception of their health status. 4024 out of 4821 subjects were enrolled, 3,899 cisgender-men (83.02%) and 125 cisgender-women (100%); all of them signed informed consent. Results: Prevalence for anti-HCV, HBsAg, anti-HIV and antiSyphilis were 0,82%, 0,15%, 0,15% and 2,55%, respectively. The average age of patients infected with HCV and HBV was 44 years old. In 31 out of 33 inmates, viral load and genotype were determined. The most prevalent genotype was 1a (71%), followed by 1b (19.3%), 3a (6,5%) and 2a/c (3.2%). 13 out of 31 (42%) received DAAs treatment, of which 9 (69%) had a sustained viral response (SVR), three did not reach SVR, and one is currently under treatment. 10 out of 31 (32%) inmates were lost to follow-up. Eight patients are waiting for their treatments. Only 1 out of 6 HBV-positive inmates had detectable viral load and is under follow-up. Conclusions: There´s a previous study in Argentina´s federal prisons (2016) on 2.277 inmates, where HCV and HBV prevalences were higher than ours (3,3% and 0,51%, respectively). Analyzing the local survey response, this gap could be due to the percentage of injection drug use: 3,13% in provincial vs. 6% in federal inmates. Checking for HCV/HBV infections in every new inmate has been adopted as a sanitary policy until nowadays.

SARS-CoV-2 variants with concerning characteristics have emerged since the end of 2020. Surveillance of SARS-CoV-2 variants was performed on a total of 4,851 samples from the capital city and 10 provinces of Argentina, during 51 epidemiological weeks (EWs) that covered the end of the first wave and the ongoing second wave of the COVID-19 pandemic in the country (EW 44/2020 to EW 41/2021). The surveillance strategy was mainly based on Sanger sequencing of a Spike coding region that allows the identification of signature mutations associated with variants. In addition, whole-genome sequences were obtained from 637 samples. The main variants found were Gamma and Lambda, and to a lesser extent, Alpha, Zeta, and Epsilon, and more recently, Delta. Whereas, Gamma dominated in different regions of the country, both Gamma and Lambda prevailed in the most populated area, the metropolitan region of Buenos Aires. The lineages that circulated on the first wave were replaced by emergent variants in a term of a few weeks. At the end of the ongoing second wave, Delta began to be detected, replacing Gamma and Lambda. This scenario is consistent with the Latin American variant landscape, so far characterized by a concurrent increase in Delta circulation and a stabilization in the number of cases. The cost-effective surveillance protocol presented here allowed for a rapid response in a resource-limited setting, added information on the expansion of Lambda in South America, and contributed to the implementation of public health measures to control the disease spread in Argentina.

Molecular surveillance of SARS-CoV-2 variants was performed on a total of 2,406 samples from the capital city and nine provinces of Argentina, during 30 epidemiological weeks (EW) that covered the end of the first wave and the beginning of the ongoing second wave of the COVID-19 pandemic in the country (EW 44/2020 to EW 20/2021). The surveillance strategy was mainly based on Sanger sequencing of a Spike coding region that allows the simultaneous identification of signature mutations associated with worldwide circulating variants. In addition, whole SARS-CoV-2 genome sequences were obtained from 456 samples. The main variants found were Gamma, Lambda and Alpha, and to a lesser extent, Zeta and Epsilon. Whereas Gamma dominated in different regions of the country, both Gamma and Lambda prevailed in the most populated area, the metropolitan region of Buenos Aires (MABA), although showing a heterogeneous distribution along this region. This cost-effective surveillance protocol allowed for a rapid response in a limited access to resources scenario, added information on the expansion of the Lambda variant in South America and contributed to the implementation of public health measures to control the disease spread in Argentina.

Background: Follow-up for anti-hepatitis A (HA) antibody persistence up to 10 years was conducted after implementation of universal vaccination against HA virus (HAV) in Mendoza, Argentina. Based on these data, statistical modeling was used to predict the antibody persistence to 30 years. Methods: A non-interventional study evaluated long-term immunogenicity (geometric mean concentrations [GMCs] and seroprotection rate) following routine vaccination with 1 dose (Group 1: N = 436) or 2 doses (Group 2: N = 108) of HA vaccine. Associated statistical modeling based on a Bayesian approach of mixed effects models on log transformed titers evaluated three models (linear, piecewise linear, and exponential decay, with and without a natural boosting effect). Results: From the initial cohort, 9 participants (Group 1) and 1 participant (Group 2) showed antibody titers below the seroprotective threshold and received a booster. At Year 10, 190 (Group 1) and 51 (Group 2) participants remained in the study without a booster dose and all were seroprotected. Regarding statistical modeling, the piecewise linear model showed the best fit and demonstrated high and similar seroprotection for each schedule up to 30 years (89% [1-dose schedule], 85% [2-dose schedule]). The 2-dose schedule showed higher GMC (95% CI) than the 1-dose schedule (Year 10: 352 [271-456] versus 78 [69.8-87.6] mltlimL) and Year 30 (predicted) (37 [13-97] versus 19 [11-34] mlU/mL). Natural boosting had little impact on predicted seroprotection rates at 30 years for the 1-dose schedule (89% [0.8-0.96] and 84% [0.73-0.94] with and without a natural booster, respectively). Conclusions: Long-term persistence of anti-HAV antibodies was observed up to 10 years with 1-dose and 2-dose vaccine schedules, supporting booster flexibility. Statistical modeling predicted good persistence of seroprotection for each schedule up to 30 years. Natural boosting had a limited impact on seroprotection rate predictions, enabling extrapolation of these results to non-endemic settings for traveler vaccination. (C) 2020 The Authors. Published by Elsevier Ltd.

Little information is available regarding the prevalence of viral hepatitis in Central West Argentina. This study aims to give new information regarding HBV and HCV prevalence, genotypes, and risk factors in Central West Argentina and the suitability of dried blood spot (DBS) sampling for HBV and HCV screening.METHODS:A total of 622 individuals were included; the mean age was 36.6 ± 14.3 years and 55.4% were females. HBV and HCV markers were detected using serological and molecular analysis, and risk factors were evaluated using statistical analysis.RESULTS:Using serum samples, the HBsAg prevalence was 1.8%, the rate of HBV exposure (anti-HBc positivity) was 5.3%, and the rate of HBV immunity was 34.9%. HBV DNA was found in four out of 11 HBsAg+ samples, and the viruses in three of these samples were classified as genotypes A1, A2 and F2a. Multivariate analysis showed that anti-HBs positivity was associated with the level of schooling and history of HBV vaccination. The anti-HCV prevalence was 2.6%, and HCV RNA was found in 11 samples, seven of which contained viruses of genotypes 1a (n = 2), 1b (n = 3) and 2 (n = 2). The sensitivity of the DBS assay for HBsAg, anti-HBc, and anti-HCV was 100%, 66.6%, and 75%, respectively, and the specificity was above 98% for all markers when compared to serum.CONCLUSION:A low rate of HBV immunity was observed, demonstrating the importance of HBV vaccination. High HCV prevalence was found, and HCV 1b was closely related to other Argentinian isolates. Finally, the performance of DBS testing in this population needs more optimization to increase its sensitivity and specificity.

This monocenter, descriptive, prospective, non-interventional study evaluated the long-term immune responses following routine vaccination with one or 2 doses of a licensed inactivated hepatitis A (HA) vaccine (Avaxim® 80U Pediatric) at age 11-23 months in a cohort of children from Mendoza, Argentina. Antibodies to hepatitis A virus (anti-HAV) were quantified annually up to Y5, and at Y7. Children whose titer decreased to below the seroprotection threshold (defined as an anti-HAV antibody concentration of ≥ 10 mIU/mL in a microparticle enzyme immunoassay up to Y5, or ≥ 3 mIU/mL in an electrochemiluminescence immunoassay at Y7) received a routine booster dose of the same HA vaccine. This report summarizes the data at 7 year after the first vaccination. Of 546 participants initially included, 264 participants remained at Y7 and provided blood samples. Of these, 204 having received one HA primary dose as a toddler were still seroprotected at Y7; titers for a further 7 also having received one HA dose as a toddler fell to below the seroprotection threshold and they therefore received a booster; all 53 having received 2 HA doses as a toddler and still present at Y7 remained seroprotected at Y7. One or 2 primary doses of this HA vaccine in toddlers result in very good persistence of anti-HAV up to 7 year post-first vaccination.

Introduction. Hepatitis E is a disease of global distribution, with significant morbidity and mortality, whose scope and burden continue to emerge in low endemic countries. Material and methods. In 2012, we studied the prevalence of anti-HEV antibodies in 202 adult serum samples. We also analyzed samples from 143 patients with acute non-A-C hepatitis from January 2011 to December 2013. Acute HEV infections were diagnosed with anti-HEV IgM and/or HEV RNA. HEV RNA was also investigated in 94 swine fecal samples. HEV RNA was sequenced and characterized. Results. We found higher values of prevalence than those previously reported in the 1990s. The overall prevalence of anti-HEV IgG antibodies was 15.4%. The prevalence was 10.6% in the 123 adults voluntarily screened on World Hepatitis Day 2012 in Buenos Aires city and 14.8, 16.7 and 35.7% respectively in the smaller groups of healthcare workers, blood donors and HIV-positive patients from different regions of the country. Nine acute HEV infections were diagnosed in the three years analyzed. We characterized new human variants of subgenotype 3a and 3i. New subgenotype 3i variants were found in swine from two distant provinces closely related to the human ones. Conclusions. These results enlarge the knowledge of HEV and contribute with new information. However, higher values of prevalence found in small groups need to be confirmed in larger studies. Many aspects of the spectrum of the disease and the reservoirs and routes of transmission are still unknown and thus deserve additional research.

Our study was conducted to further investigate the single-dose approach of hepatitis A vaccination, while providing supportive data on the flexibility of booster administration. Participants received at least one dose of Avaxim 80U Pediatric at 11-23 months of age, and they will be followed for 10 years. We report here the fourth and fifth years after the first vaccination. Group assignment was based on whether the children received 1 dose and no booster during the study (Group 1) or 2 doses and no further booster (Group 2). Anti-HAV antibody concentrations were assessed at each annual visit. Of the 546 initial participants, 441 (80.8%) and 412 (75.5%) were followed up 4 and 5 years after vaccination, respectively. Of the 411 subjects evaluable at Year 5, 318 had received one vaccine dose and 85 had received two. Seroprotection rates were still high in Group 1 (99.7%) and in Group 2 (100%) 5 years after one or two doses of Avaxim 80U Pediatric, correspondingly. Anti-HAV geometric mean concentrations decreased in both groups compared to what they were 3 years after vaccination, while remaining well above the 10 mIU/mL threshold 5 years after vaccination. The highest concentrations were found in the children who received 2 vaccine doses. Hepatitis A humoral immunity induced by a single dose of inactivated hepatitis A vaccine can persist for at least 5 years in a paediatric population. The study results also support recommendations in favour of a flexible time window for booster vaccination.

BACKGROUND:This study was done to determine the immunogenicity of a single dose of hepatitis A vaccine in children, providing needed clinical data on the flexibility of booster administration. METHODS:Participants had received one dose of inactivated hepatitis A vaccine (Avaxim™ 80 U Pediatric) at 12-23 months of age or two doses of the same vaccine at 12 and 18 months of age prior to enrolment. Anti-hepatitis A antibody concentrations were measured at the first, second, and third year after vaccination. Suspected cases of hepatitis A in participant families were assessed and family socioeconomic data were collected. RESULTS:A series of 546 participants were enrolled. Of 467 (85.5%) participants completing 3 years of follow-up, 365 had received a single vaccine dose and 94 had received two vaccine doses. Seropositivity (anti-HAV ≥ 10 mIU/mL) at 3 years was 99.7% after one dose and 100% after two doses. At one year, geometric mean concentrations were higher after two doses (1433.9 mIU/mL, 95% confidence interval [CI] 1108-1855) than one (209.7 mIU/mL, 95% CI 190.6-230.6). Geometric mean concentrations decreased in both groups during the study, but remained well above 10 mIU/mL through the third year. The geometric mean of 3-year to one-year anti-hepatitis A concentration ratios was 0.74 (95% CI 0.70-0.79) following one dose and 0.57 (95% CI 0.47-0.70) following two doses. The greatest decrease in geometric mean concentrations occurred during the third year, ie, 21.2% in the one-dose group and 40.8% in the two-dose group. Six participants became seronegative during follow-up and responded strongly to a booster dose. Anti-hepatitis A concentrations increased in 135 children (34.9%) in the second year and 50 (13.7%) in the third year; none lived in a family with a case of hepatitis A. Three confirmed cases of hepatitis A occurred in family members. Participants belonged to a middle-income, urban/suburban population with good sanitation facilities and water supplies. CONCLUSION:A single dose of hepatitis A vaccine at 12-23 months of age resulted in hepatitis A seropositivity in all but one vaccinee after 3 years. Increased anti-hepatitis A serum concentrations suggested exposure to wild-type hepatitis A virus in this middle-class socioeconomic environment. Continuing surveillance is required to confirm the effectiveness of a single-dose hepatitis A vaccination; however, the results of the first three years are encouraging.

Hacia fines del ano 2003, en la ciudad de Ushuaia resulto llamativa la cantidad de ninos internados con cuadros respiratorios graves y estudios virologicos negativos. Sobre la base de publicaciones acerca de la circulacion de un nuevo virus respiratorio, metapneumovirus humano, se decidio investigar su presencia en tres muestras respiratorias de ninos internados con infeccion respiratoria aguda en el Hospital Regional de Ushuaia. Los aspirados nasofaringeos, previamente negativos para los virus respiratorios comunes por la tecnica de inmunofluorescencia, fueron estudiados mediante la tecnica de transcripcion inversa y amplificacion genomica por reaccion en cadena de la polimerasa para metapneumovirus humano. Una de las muestras resulto positiva para metapneumovirus humano. En ninguno de los pacientes se detectaron anticuerpos de clase IgM para Chlamydia spp y Mycoplasma pneumoniae,por la tecnica de inmunofluorescencia. La descripcion del presente caso enfatiza la necesidad de ampliar el espectro diagnostico en ninos internados que resulten negativos para los virus respiratorios mas comunes.

Among viral agents causing gastroenteritis, human astroviruses (HAstVs) take second or third place, after rotaviruses and caliciviruses, as the most frequent cause of illness. The aims of this study were to determine the prevalence of HAstV infection and to characterize the circulating HAstV strains in children with diarrhea under 3 years of age treated between 1995 and 1998 at out- or in-patient facilities of the children's hospital in Mendoza, Argentina. Reverse transcription-polymerase chain reaction (RT-PCR) and enzyme immunoassay (EIA) were used to detect HAstVs in stool specimens. Positive specimens were tested further by EIA and/or sequenced to type detected HAstV strains. HAstVs were detected in 40 (3.7%) of 1,070 samples that were rotavirus and calicivirus-negative: 14 (3.5%) of 402 from outpatients and 26 (3.9%) of 668 from inpatients. HAstV infection tended to be more severe in children during their first year of life: 18 (4.7%) of 383 HAstV-positive children 0-11 months old were hospitalized versus 8 (2.8%) of 285 children 1 year of age or older (P = 0.29). Type 1 (HAstV-1) was the most common type (41%), followed by HAstV-4 (25%), HAstV-2 (13%), HAstV-3 (13%), and HAstV-5 (8%). In this first epidemiological study of HAstV infection in this region, we confirmed HAstV to be a cause of severe gastroenteritis in children, more often among children younger than 12 months of age. HastV-4 caused 25% of HastV infections in Mendoza, although it has been detected commonly elsewhere. Distinct genetic lineages were apparent but their epidemiological significance remains to be demonstrated.

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. J. Med. Virol. 67:289–298, 2002. © 2002 Wiley‐Liss, Inc.

RSV is a major cause of morbidity in all the countries where it has been investigated. However, there is not enough data to evaluate its importance in the hospitalization of high risk infants and children (low birthweight, premature birth, bronchopulmonory displasia, or uncorrected congenital heart disease). An epidemiological, multicenter, non-intervention study to determine the prevalence of RSV in high risk children who report to an emergency room was developed. Forty seven children were included during May to October 2001. RSV was confirmed in 65.9% of them. All RSV positive children were hospitalized for an average of 9 days and 40% required the use of ventilator. Two children died. In the group of RSV negative children 81.2% were hospitalized for an average of 5 days and no ventilator was needed. No deaths were registered. It should be necessary to extend this kind of studies in Argentina in order to collect more data to find appropriate ways to control the impact of RSV infections in high risk children.

Group A rotaviruses are the major cause of severe gastroenteritis in young children worldwide. Because rotavirus vaccination appeared imminent, a nationwide surveillance program was organized between October 1996 and October 1998 in the largest Argentine cities. Surveillance for disease burden, rotavirus detection, and rotavirus typing was undertaken at nine locations. Results showed rotavirus to be associated with 42% of diarrhea admissions. Although the prevalent G types changed from year to year, common G types were found in 96% of the cases and were usually associated with common P types. Uncommon G types, G9 and G5, were found at low prevalence and uncommon G/P combinations occurred at almost every study site. These data suggest that a rotavirus vaccine could substantially decrease the rotavirus disease burden in Argentina, but that introduction of a vaccine should be accompanied by a concurrent surveillance system. J. Med. Virol. 65:190–198, 2001. © 2001 Wiley‐Liss, Inc.

Knowledge of the antigenic diversity of rotaviruses circulating in a region should be acquired before introducing a rotavirus vaccine. In a collection of 151 rotavirus-positive samples from Mendoza, Argentina, strain diversity was evaluated utilizing G-typing monoclonal antibodies (MAbs), reverse-transcriptase-polymerase chain reaction (RT-PCR) G and P typing, and electropherotyping (PAGE). The G type of 137 (91%) specimens was determined. Typing MAb reactivity with the homologous type ranged from 25-94%. For the seven G1 MAbs utilized, 28 patterns of reactivity among 68 G1 strains occurred. For the 48 G2 strains, six patterns of reactivity occurred utilizing three G2-specific MAbs. Of the 92 samples G- and P-typed by reverse-transcriptase-polymerase chain reaction, 89% had single G/P combinations: eight G1[P4], one G1[P6], twelve G1[P8], 58 G2 [P4], and two G2 [P6]. Nine samples had more than one G type with a single P type, one sample had two P types associated with one G type, and one sample contained multiple G and P types. Twenty-nine PAGE patterns occurred for all G types, but differences of antigenic reaction did not predict differences in migration of gene segments 7, 8, and 9. For three specimens showing discordant results between G type by enzyme-linked immunosorbent assay (EIA) and RT-PCR, we observed unexpected electropherotypes. Complementary evaluation by RT-PCR and MAb-based EIA with multiple typing MAbs revealed genetic and antigenic diversity of circulating rotaviruses, including extensive intratypic variation of the G1 and G2 neutralization antigens, in Mendoza during a single season of rotavirus activity.