Comparison of SARS-CoV-2 viral load in asymptomatic and symptomatic children attended in a referral public pediatric hospital in Argentina / Comparación de la carga viral de SARS-CoV-2 en niños asintomáticos y sintomáticos atendidos en un hospital pediátrico público de referencia en Argentina

Abstract At present, different reports have shown that children reach similar SARS-CoV-2 viral load (VL) levels compared to adults; however, the impact of VL on children remains ambiguous when asymptomatic versus symptomatic cases are compared. Thus, the aim of this study was to assess VL at the time of diagnosis in asymptomatic and symptomatic SARS-CoV-2 infected children. VL analysis was retrospectively carried out from nasopharyngeal swabs on 82 SARS-CoV-2 infected children, from March to October 2020. Of the 82 children, 31 were asymptomatic. Symptomatic patients had significantly higher VL values compared to asymptomatic ones (median = 7.41 vs4.35 log10 copies/ml, respectively). Notwithstanding, 8 out of 31 asymptomatic children had high VL levels, overlapping levels observed above the first quartile in the symptomatic group. Analysis of different age groups revealed that median VL values were higher in the symptomatic groups, although there was only a significant difference in children younger than 5 years of age. On the other hand, there was no significant difference between the VL values from the 82 SARS-CoV-2 infected children according to age, sex, underlying disease, symptoms or severity of COVID-19 related disease. This study emphasizes the importance of VL analysis in SARS-CoV-2 infected children, who could contribute to viral spread in the community. This concern could be extended to healthcare workers, who are in contact with children.

Resumen Diferentes informes han demostrado que los ninos alcanzan niveles de carga viral (CV) de SARS-CoV-2 similares a los de los adultos, pero el impacto de la CV en los niños continua siendo incierto cuando se compara entre aquellos que son asintomáticos y sintomáticos. El objetivo de este estudio fue evaluar la CV al momento del diagnóstico en ninos asintomáticos y sintomáticos infectados por SARS-CoV-2. El análisis de CV se realizó retrospectivamente a partir de muestras de hisopados nasofaríngeos de 82 niños infectados por SARS-CoV-2 entre marzo y octubre de 2020. De ellos, 31 eran asintomáticos. Encontramos que el grupo sintomático tenía valores de CV significativamente más altos en comparación con el grupo asintomático (mediana = 7,41 vs. 4,35 log10 copias/ml, respectivamente). No obstante, 8 de los 31 ninos asintomáticos presentaron valores de CV elevados, equivalentes a los observados por encima del primer cuartil del grupo sintomático. El análisis por grupos de edad reveló que la mediana de CV fue más alta en los niños sintomáticos, aunque esta diferencia fue significativa solamente en los menores de 5 anos. A su vez, los valores de CV obtenidos a partir de los 82 niños infectados por SARS-CoV-2 no mostraron diferencias significativas según el grupo etario, el sexo, la enfermedad de base, los síntomas y la gravedad de la COVID-19. Este estudio enfatiza la necesidad del análisis de la CV en ninos infectados por SARS-CoV-2, quienes podrían contribuir a la propagación del virus en la comunidad. Esta preocupación podría extenderse a los trabajadores de la salud que están en contacto con los ninños.

COVID-19 in immunocompromised children: comparison of SARS-CoV-2 viral load dynamics between the first and third waves.

SARS-CoV-2 dynamics across different COVID-19 waves has been unclear in immunocompromised children. We aimed to compare the dynamics of SARS-CoV-2 RNA viral load (VL) during the first and third waves of COVID-19 in immunocompromised children. A retrospective and longitudinal cohort study was conducted in a pediatric referral hospital of Argentina. The study included 28 admitted immunocompromised children with laboratory confirmed SARS-CoV-2 infection. Thirteen acquired the infection during COVID-19 first wave (May to August 2020, group 1 (G1)) and fifteen in the third wave (January to March 2022, group 2 (G2)). RNA viral load measure and its dynamic reconstruction were performed in nasopharyngeal swabs by validated quantitative, real time RT-PCR, and linear mixed-effects model, respectively. Of the 28 children included, 54% were girls, most of them had hemato-oncological pathology (57%), and the median age was 8 years (interquartile range (IQR): 3-13). The dynamic of VL was similar in both groups (P = 0.148), starting from a level of 5.34 log10 copies/mL (95% confidence interval (CI): 4.47-6.21) in G1 and 5.79 log10 copies/mL (95% CI: 4.93-6.65) in G2. Then, VL decayed with a rate of 0.059 (95% CI: 0.038-0.080) and 0.088 (95% CI: 0.058-0.118) log10 copies/mL per day since diagnosis and fell below the limit of quantification at days 51 and 39 after diagnosis in G1 and G2, respectively. Our results evidenced a longer viral RNA persistence in immunocompromised pediatric patients and no difference in VL dynamic between COVID-19 first wave-attributed to ancestral infections-and third wave-attributed to Omicron infections.

Comparison of SARS-CoV-2 viral load in asymptomatic and symptomatic children attended in a referral public pediatric hospital in Argentina.

At present, different reports have shown that children reach similar SARS-CoV-2 viral load (VL) levels compared to adults; however, the impact of VL on children remains ambiguous when asymptomatic versus symptomatic cases are compared. Thus, the aim of this study was to assess VL at the time of diagnosis in asymptomatic and symptomatic SARS-CoV-2 infected children. VL analysis was retrospectively carried out from nasopharyngeal swabs on 82 SARS-CoV-2 infected children, from March to October 2020. Of the 82 children, 31 were asymptomatic. Symptomatic patients had significantly higher VL values compared to asymptomatic ones (median=7.41 vs 4.35log10 copies/ml, respectively). Notwithstanding, 8 out of 31 asymptomatic children had high VL levels, overlapping levels observed above the first quartile in the symptomatic group. Analysis of different age groups revealed that median VL values were higher in the symptomatic groups, although there was only a significant difference in children younger than 5 years of age. On the other hand, there was no significant difference between the VL values from the 82 SARS-CoV-2 infected children according to age, sex, underlying disease, symptoms or severity of COVID-19 related disease. This study emphasizes the importance of VL analysis in SARS-CoV-2 infected children, who could contribute to viral spread in the community. This concern could be extended to healthcare workers, who are in contact with children.

Case Report: Hyperinflammatory Status in an Immunocompromised Child With a Highly Sustained Viral Load of SARS-CoV-2.

Coronavirus disease 2019 (COVID-19) is spreading throughout the world. Limited data are available for the dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load (VL) in immunocompromised pediatric patients. Here, we report the clinical characteristics and the dynamics of SARS-CoV-2 VL of a pediatric patient with acute myeloid leukemia who developed a hyperinflammatory status mimicked MIS-C. The clinical course was characterized by the late onset of fever, GI symptoms, rash, and respiratory distress, including oxygen requirement with sustained VL of SARS-CoV-2 around 7 log10 RNA copies/mL for 6 weeks. It is important to note that the hyperinflammatory status developed early at the third week of hospitalization-in a context of high VL and immunocompromised status. All these characteristics make this clinical case unique. On the other hand, while many reports have characterized the dynamics of SARS-CoV-2 VL in adults and immunocompetent hosts, it remains unreported in pediatrics-even less in immunosuppressed children.

Corrigendum to Antiviral effect of high-dose ivermectin in adults with COVID-19: A proof-of-concept randomized trial [EClinicalMedicine 37 (2021) 100,959]".

[This corrects the article DOI: 10.1016/j.eclinm.2021.100959.].

A new highly sensitive single-tube nested real-time PCR assay: Clinical utility in perinatal HIV-1 diagnosis.

Real time PCR is one of the major tools for molecular diagnosis, however not always reaches the required sensitivity, especially in detecting early infectious disease. To overcome this problem, nested PCR is commonly performed, since it is highly sensitive, but it is time-consuming, prone to cross-contamination and difficult to standardize. Therefore, we developed a sensitive and specific single-tube nested real-time PCR (STN-real-time PCR) assay and evaluated its clinical utility on early infant HIV-1 diagnosis (EID). The STN-real-time PCR enables the simultaneous amplification of four HIV-1 specific amplicons by the use of an internal and external pair of primers targeting ltr/gag region, and another one corresponding to human albumin as an internal control. Thermocycling had different annealing temperatures to favor the sequential use of each pair of primers, and included an initial touchdown step to broaden specificity and increase sensitivity. Finally, HIV-1 was detected by melting curve analysis. A total of 234 samples collected retrospectively and prospectively from HIV-1 exposed infants aged <18 months were used to evaluate the performance of the assay and compare it with a routine diagnostic nested-multiplex PCR. The developed assay had a limit of detection of 3 copies of HIV-1 DNA per reaction and had a sensitivity of 31 % more than routine diagnostic nested-multiplex PCR when testing samples near delivery. In conclusion, we developed a new assay by turning a conventional nested-PCR into a faster, more sensitive and feasible STN-real-time PCR assay for EID and potentially useful for detection of pathogens with variable genomes and present in low copy numbers.

Antiviral effect of high-dose ivermectin in adults with COVID-19: A proof-of-concept randomized trial.

BACKGROUND: There are limited antiviral options for the treatment of patients with COVID-19. Ivermectin (IVM), a macrocyclic lactone with a wide anti-parasitary spectrum, has shown potent activity against SARS-CoV-2 in vitro. This study aimed at assessing the antiviral effect of IVM on viral load of respiratory secretions and its relationship with drug concentrations in plasma. METHODS: Proof-of-concept, pilot, randomized, controlled, outcome-assessor blinded trial to evaluate antiviral activity of high-dose IVM in 45 COVID-19 hospitalized patients randomized in a 2:1 ratio to standard of care plus oral IVM at 0·6 mg/kg/day for 5 days versus standard of care in 4 hospitals in Argentina. Eligible patients were adults with RT-PCR confirmed SARS-CoV-2 infection within 5 days of symptoms onset. The primary endpoint was the difference in viral load in respiratory secretions between baseline and day-5, by quantitative RT-PCR. Concentrations of IVM in plasma were measured. Study registered at ClinicalTrials.gov: NCT04381884. FINDINGS: 45 participants were recruited (30 to IVM and 15 controls) between May 18 and September 9, 2020. There was no difference in viral load reduction between groups but a significant difference was found in patients with higher median plasma IVM levels (72% IQR 59-77) versus untreated controls (42% IQR 31-73) (p = 0·004). Mean ivermectin plasma concentration levels correlated with viral decay rate (r: 0·47, p = 0·02). Adverse events were similar between groups. No differences in clinical evolution at day-7 and day-30 between groups were observed. INTERPRETATION: A concentration dependent antiviral activity of oral high-dose IVM was identified at a dosing regimen that was well tolerated. Large trials with clinical endpoints are necessary to determine the clinical utility of IVM in COVID-19. FUNDING: This work was supported by grant IP-COVID-19-625, Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación, Argentina and Laboratorio ELEA/Phoenix, Argentina.

Unraveling HIV-1 diagnosis in special pediatric cases.

BACKGROUND: Early HIV-1 diagnosis and initiation of antiretroviral treatment is essential to prevent AIDS, and reduce mortality in children. HIV-1 molecular diagnosis in children before 18 months of age require, two independent samples to confirm a result. However, some patients have discordant virologic results in different samples, raising uncertainty for a conclusive diagnosis. We defined these patients as "special pediatric cases". OBJECTIVES: The aim of our study was to characterize the "special pediatric cases" among HIV-1 infected children diagnosed in a five-year period at our laboratory and evaluate the impact on the time to HIV-1 diagnosis. STUDY DESIGN: A total of 44 perinatally HIV-1 infected infants with molecular diagnostic performed at the Pediatric Garrahan Hospital were analyzed from 2013 to 2017. RESULTS: We identified eight "special pediatric cases". In the first samples, all of them had negative results by different DNA-PCR assays. Three infants had undetectable plasma viral load (pVL), four had low detectable pVL value, and one infant had no available pVL. All samples with detectable pVL, including those with low pVL (ie: 65copies/mL), had high pVL values at the end of the diagnosis. Considering the age of the HIV-1 infected children at the end of the diagnosis, five "special pediatric cases" (62 %) had a "late" positive diagnosis [mean (range) = 146 (89-268) days old]. CONCLUSIONS: These "special pediatric cases" are not as unusual as previously thought and are important diagnostic challenges. Also, this study add evidence to include the viral load assay in the molecular diagnostic algorithm for perinatal HIV-1 infection.

Pre-treatment drug resistance and HIV-1 subtypes in infants from Argentina with and without exposure to antiretroviral drugs for prevention of mother-to-child transmission.

OBJECTIVES: To assess the prevalence and patterns of pre-treatment HIV drug resistance (PDR) and HIV-1 subtype in infants from Argentina with exposure to different antiretroviral drugs (ARVs) for the prevention of mother-to-child transmission (PMTCT). PATIENTS AND METHODS: HIV-1 genotyping was performed in 115 infants (median age = 2.3 months) born between 2007 and 2014 to screen for drug resistance mutations (DRMs) before starting first-line ART. HIV-1 subtype was characterized by phylogenetic and recombination analysis. RESULTS: Overall, DRMs were found in 34 of 115 infants (PDR level 30% to any ARV, 3.5% to PIs, 12% to NRTIs and 22% to NNRTIs). Of the 115 infants, 22 (19.1%) were ARV-unexposed. Another 93 were ARV-exposed: 28 (24.3%) to short-course zidovudine monotherapy ARV prophylaxis; 25 (21.7%) to nevirapine-based ARV prophylaxis; 12 (10.4%) to perinatal infant zidovudine prophylaxis + maternal combination ART with NNRTIs; and 28 (24.3%) to perinatal infant zidovudine prophylaxis+maternal combination ART with PIs. Transmitted drug resistance among ARV-unexposed infants was 32% (5% to PIs, 9% to NRTIs and 18% to NNRTIs). ART-exposed infants showed multi-class ARV resistance. Importantly, vertical transmission of a triple-class-resistant virus was confirmed in one case. Patterns of DRMs predicted high-level resistance to NNRTIs in a similar and high proportion (>50%) of infants with at least one DRM independently of ARV exposure. BF recombinants were found in 74%, subtype B in 20%, subtype C in 3% and novel AG and AB recombinants in 3%. CONCLUSIONS: PDR in HIV-1-infected children from Argentina is among the highest reported, jeopardizing successful lifelong suppressive ART as well as the efficacy of current PMTCT regimens.

Microbial and viral-like rhodopsins present in coastal marine sediments from four polar and subpolar regions.

Rhodopsins are broadly distributed. In this work, we analyzed 23 metagenomes corresponding to marine sediment samples from four regions that share cold climate conditions (Norway; Sweden; Argentina and Antarctica). In order to investigate the genes evolution of viral rhodopsins, an initial set of 6224 bacterial rhodopsin sequences according to COG5524 were retrieved from the 23 metagenomes. After selection by the presence of transmembrane domains and alignment, 123 viral (51) and non-viral (72) sequences (>50 amino acids) were finally included in further analysis. Viral rhodopsin genes were homologs of Phaeocystis globosa virus and Organic lake Phycodnavirus. Non-viral microbial rhodopsin genes were ascribed to Bacteroidetes, Planctomycetes, Firmicutes, Actinobacteria, Cyanobacteria, Proteobacteria, Deinococcus-Thermus and Cryptophyta and Fungi. A rescreening using Blastp, using as queries the viral sequences previously described, retrieved 30 sequences (>100 amino acids). Phylogeographic analysis revealed a geographical clustering of the sequences affiliated to the viral group. This clustering was not observed for the microbial non-viral sequences. The phylogenetic reconstruction allowed us to propose the existence of a putative ancestor of viral rhodopsin genes related to Actinobacteria and Chloroflexi. This is the first report about the existence of a phylogeographic association of the viral rhodopsin sequences from marine sediments.

Molecular Epidemiology and Spatio-Temporal Dynamics of the H3N8 Equine Influenza Virus in South America.

Equine influenza virus (EIV) is considered the most important respiratory pathogen of horses as outbreaks of the disease lead to substantial economic losses. The H3N8 EIV has caused respiratory disease in horses across the world, including South American countries. Nucleotide and deduced amino acid sequences for the complete haemagglutinin gene of the H3N8 EIV detected in South America since 1963 were analyzed. Phylogenetic and Bayesian coalescent analyses were carried out to study the origin, the time of the most recent common ancestors (tMRCA), the demographic and the phylogeographic patterns of the H3N8 EIV. The phylogenetic analysis demonstrated that the H3N8 EIV detected in South America grouped in 5 well-supported monophyletic clades, each associated with strains of different origins. The tMRCA estimated for each group suggested that the virus was circulating in North America at least one year before its effective circulation in the South American population. Phylogenetic and coalescent analyses revealed a polyphyletic behavior of the viruses causing the outbreaks in South America between 1963 and 2012, possibly due to the introduction of at least 4 different EIVs through the international movement of horses. In addition, phylodynamic analysis suggested South America as the starting point of the spread of the H3N8 EIV in 1963 and showed migration links from the United States to South America in the subsequent EIV irruptions. Further, an increase in the relative genetic diversity was observed between 2006 and 2007 and a subsequent decline since 2009, probably due to the co-circulation of different lineages and as a result of the incorporation of the Florida clade 2 strain in vaccines, respectively. The observed data highlight the importance of epidemiological surveillance and the implementation of appropriate quarantine procedures to prevent outbreaks of the disease.

Identification, molecular and phylogenetic analysis of poxvirus in skin lesions of southern right whale.

Poxvirus skin disease has been reported in several species of cetaceans, principally in odontocetes, and a single report in mysticetes. Southern right whales Eubalaena australis in Peninsula Valdes, Argentina, show a variety of skin lesions of unknown etiology, and the number of these lesions has increased in recent years. Samples from dead whales were taken in order to establish the etiology of these lesions. One calf and one adult presented ring-type lesions, characterized by a circumscribed and slightly raised area of skin. Lesions were histologically characterized by the presence of microvesicles and vacuolated cells in the stratum spinosum, along with hyperplasia of the stratum corneum and eosinophilic inclusion bodies in the cytoplasm of the epithelial cells. Transmission electron microscopy showed aggregations of virions with typical poxvirus morphology. PCR of cetacean poxvirus (CPV) DNA polymerase, DNA topoisomerase I and parapoxvirus DNA polymerase gene fragments was done, and confirmed the presence of poxvirus in one sample. Phylogenetic analysis showed that the detected poxvirus belongs to the CPV-2 group. This is the first confirmed report of poxvirus in southern right whales in Argentina.

Short communication: Emergence of novel A/G recombinant HIV-1 strains in Argentina.

The predominant circulating HIV-1 strains in South America are subtype B and B/F recombinants with different distributions among countries. However, the emergence of other subtypes is a matter of concern and needs continuous monitoring. We identified three different A/G recombinants in Argentina, two of them in vertically infected children from unlinked mothers and one in an adult female. HIV-1 pol sequences from the children showed novel A/G recombination patterns and no phylogenetic relationship with previously reported South American A/G sequences. The third A/G recombinant was a CRF06_cpx with African origin. The detection of new or unusual subtypes is important to avoid false-negative PCR HIV-1 early diagnosis due to detection failures and for future vaccine development.

Rich bacterial assemblages from Maritime Antarctica (Potter Cove, South Shetlands) reveal several kinds of endemic and undescribed phylotypes.

Bacterial richness in maritime Antarctica has been poorly described to date. Phylogenetic affiliation of seawater free-living microbial assemblages was studied from three locations near the Argentinean Jubany Station during two Antarctic summers. Sixty 16S RNA cloned sequences were phylogenetically affiliated to Alphaproteobacteria (30/60 clones), Gammaproteobacteria(19/60 clones), Betaproteobacteria and Cytophaga-Flavobacteriia-Bacteroides (CFB), which were (2/60) and (3/60) respectively. Furthermore, six out of 60 clones could not be classified. Both, Alphaproteobacteria and Gammaproteobacteria, showed several endemic and previously undescribed sequences. Moreover, the absence of Cyanobacteria sequences in our samples is remarkable. In conclusion, we are reporting a rich sequence assemblage composed of widely divergent isolates among themselves and distant from the most closely related sequences currently deposited in data banks.

Rich bacterial assemblages from Maritime Antarctica (Potter Cove, South Shetlands) reveal several kinds of endemic and undescribed phylotypes / Una rica colección de bacterias marinas antárticas (Caleta Potter, islas Shetlands del Sur) revela diversos filotipos endémicos y previamente no descritos

.

Bacterial richness in maritime Antarctica has been poorly described to date. Phylogenetic affiliation of seawater free-living microbial assemblages was studied from three locations near the Argentinean Jubany Station during two Antarctic summers. Sixty 16S RNA cloned sequences were phylogenetically affiliated to Alphaproteobacteria (30/60 clones), Gammaproteobacteria(19/60 clones), Betaproteobacteria and Cytophaga-Flavobacteriia- Bacteroides (CFB), which were (2/60) and (3/60) respectively. Furthermore, six out of 60 clones could not be classified. Both, Alphaproteobacteria and Gammaproteobacteria, showed several endemic and previously undescribed sequences. Moreover, the absence of Cyanobacteria sequences in our samples is remarkable. In conclusion, we are reporting a rich sequence assemblage composed of widely divergent isolates among themselves and distant from the most closely related sequences currently deposited in data banks.

Rich bacterial assemblages from Maritime Antarctica (Potter Cove, South Shetlands) reveal several kinds of endemic and undescribed phylotypes / Una rica colección de bacterias marinas antárticas (Caleta Potter, islas Shetlands del Sur) revela diversos filotipos endémicos y previamente no descritos

.(AU)

Bacterial richness in maritime Antarctica has been poorly described to date. Phylogenetic affiliation of seawater free-living microbial assemblages was studied from three locations near the Argentinean Jubany Station during two Antarctic summers. Sixty 16S RNA cloned sequences were phylogenetically affiliated to Alphaproteobacteria (30/60 clones), Gammaproteobacteria(19/60 clones), Betaproteobacteria and Cytophaga-Flavobacteriia- Bacteroides (CFB), which were (2/60) and (3/60) respectively. Furthermore, six out of 60 clones could not be classified. Both, Alphaproteobacteria and Gammaproteobacteria, showed several endemic and previously undescribed sequences. Moreover, the absence of Cyanobacteria sequences in our samples is remarkable. In conclusion, we are reporting a rich sequence assemblage composed of widely divergent isolates among themselves and distant from the most closely related sequences currently deposited in data banks.(AU)

Spreading of hepatitis C virus subtypes 1a and 1b through the central region of Argentina.

The recent history of the hepatitis C virus (HCV) subtypes 1a and 1b in the central region of Argentina is hypothesized by phylogeographic reconstruction using coalescent based Bayesian analyses. Direct partial E2 sequences from HCV 1a and 1b infected patients attending different health-care centers of the country were analyzed. The inferred date of the most recent common ancestor (tMRCA) for HCV-1a was: 1962 (between 1943 and 1977) and for HCV-1b was earlier: 1929 (between 1895 and 1953). Diverse ancestral populations were inferred from both subtypes in Córdoba and in Buenos Aires cities and after that, HCV spread within and between larger cities and to other smaller cities. The analyses suggested that HCV-1b was dispersed first and it is currently in a stationary phase whereas HCV-1a was dispersed latter and it is still in a growth phase. Finally, as it was observed in the developed countries, while the transmission of HCV-1b appears to have been somehow prevented, the HCV-1a may still represent a concern in the public health. Further work should be carried out to address their current transmission rate (and its main transmission route) in the Argentinean population.

Rich bacterial assemblages from Maritime Antarctica (Potter Cove, South Shetlands) reveal several kinds of endemic and undescribed phylotypes. / Rich bacterial assemblages from Maritime Antarctica (Potter Cove, South Shetlands) reveal several kinds of endemic and undescribed phylotypes.

Bacterial richness in maritime Antarctica has been poorly described to date. Phylogenetic affiliation of seawater free-living microbial assemblages was studied from three locations near the Argentinean Jubany Station during two Antarctic summers. Sixty 16S RNA cloned sequences were phylogenetically affiliated to Alphaproteobacteria (30/60 clones), Gammaproteobacteria(19/60 clones), Betaproteobacteria and Cytophaga-Flavobacteriia-Bacteroides (CFB), which were (2/60) and (3/60) respectively. Furthermore, six out of 60 clones could not be classified. Both, Alphaproteobacteria and Gammaproteobacteria, showed several endemic and previously undescribed sequences. Moreover, the absence of Cyanobacteria sequences in our samples is remarkable. In conclusion, we are reporting a rich sequence assemblage composed of widely divergent isolates among themselves and distant from the most closely related sequences currently deposited in data banks.

Hepatitis C virus diversification in Argentina: comparative analysis between the large city of Buenos Aires and the small rural town of O'Brien.

BACKGROUND: The estimated prevalence of HCV infection in Argentina is around 2%. However, higher rates of infection have been described in population studies of small urban and rural communities. The aim of this work was to compare the origin and diversification of HCV-1b in samples from two different epidemiological scenarios: Buenos Aires, a large cosmopolitan city, and O'Brien, a small rural town with a high prevalence of HCV infection. PATIENTS AND METHODS: The E1/E2 and NS5B regions of the viral genome from 83 patients infected with HCV-1b were sequenced. Phylogenetic analysis and Bayesian Coalescent methods were used to study the origin and diversification of HCV-1b in both patient populations. RESULTS: Samples from Buenos Aires showed a polyphyletic behavior with a tMRCA around 1887-1900 and a time of spread of infection approximately 60 years ago. In contrast, samples from ÓBrien showed a monophyletic behavior with a tMRCA around 1950-1960 and a time of spread of infection more recent than in Buenos Aires, around 20-30 years ago. CONCLUSION: Phylogenetic and coalescence analysis revealed a different behavior in the epidemiological histories of Buenos Aires and ÓBrien. HCV infection in Buenos Aires shows a polyphyletic behavior and an exponential growth in two phases, whereas that in O'Brien shows a monophyletic cluster and an exponential growth in one single step with a more recent tMRCA. The polyphyletic origin and the probability of encountering susceptible individuals in a large cosmopolitan city like Buenos Aires are in agreement with a longer period of expansion. In contrast, in less populated areas such as O'Brien, the chances of HCV transmission are strongly restricted. Furthermore, the monophyletic character and the most recent time of emergence suggest that different HCV-1b ancestors (variants) that were in expansion in Buenos Aires had the opportunity to colonize and expand in O'Brien.

High prevalence of hepatitis C virus genotype 1b infection in a small town of Argentina. Phylogenetic and Bayesian coalescent analysis.

Previous studies in Argentina have documented a general prevalence of Hepatitis C Virus (HCV) infection close to 2%. In addition, a high prevalence of HCV has been recently reported in different Argentinean small rural communities. In this work, we performed a study aimed at analyzing the origins and diversification patterns of an HCV outbreak in Wheelwright, a small rural town located in Santa Fe province (Argentina).A total of 89 out of 1814 blood samples collected from people living in Wheelwright, were positive for HCV infection. The highest prevalence (4.9%) was observed in people older than 50 years, with the highest level for the group aged between 70-79 years (22%). The RFLP analyses showed that 91% of the positive samples belonged to the HCV-1b genotype. The E1/E2 and NS5B genes were sequenced, and their phylogenetic analysis showed that the HCV-1b sequences from Wheelwright were monophyletic. Bayesian coalescent-based methods were used to estimate substitution rates and time of the most recent common ancestor (tMRCA). The mean estimated substitution rates and the tMRCA for E1/E2 with and without HVR1 and NS5B were 7.41E-03 s/s/y and 61 years, 5.05E-03 s/s/y and 58 years and 3.24E-03 s/s/y and 53 years, respectively. In summary, the tMRCA values, the demographic model with constant population size, and the fact that the highest prevalence of infection was observed in elder people support the hypothesis that the HCV-1b introduction in Wheelwright initially occurred at least five decades ago and that the early epidemic was characterized by a fast rate of virus transmission. The epidemic seems to have been controlled later on down to the standard transmission rates observed elsewhere.