Daniel Oscar Alonso

In this work, we performed the genetic characterization of a new variant of orthohantavirus associated with a fatal case of hantavirus pulmonary syndrome, outside the known endemic region, in northwestern Argentina. We first confirmed an orthohantavirus infection by ELISA, testing for the detection of IgM and IgG antibodies. Then, we extracted RNA from 100 microliters of serum, the only sample available, followed by RT-PCR. The amplicons were sequenced using Sanger and next-generation sequencing technology. We obtained partial sequences of 1253 bp, 799 bp and 1675 bp from the S-, M- and L-segments, respectively, showing low sequence identities with all the previously characterized hantaviruses (10.9%, 13.5% and 15.1% of the divergence, respectively). The phylogenetic analysis showed that this virus belongs to the Orthohantavirus andesense species (ANDV), and among the ANDV-like variants, it is more closely related to the Lechiguanas clade. Similar percentages of divergence were considered sufficient to distinguish AND-like variants in previous works. As the patient had no travel history before the onset of disease was reported, we conducted rodent surveys to confirm the presence of reservoirs. The rodent assemblage was compatible with the transitional zone among different ecoregions (Yungas, Chaco and Monte). Moreover, one of the species captured, Oligoryzomys flavescens, was previously described as a reservoir of hantavirus. This species may either host several variants across its range or encompass a species complex, as proposed by some authors.

Hantavirus Pulmonary Syndrome (HPS), characterized by its high fatality rate, poses a significant public health concern in Argentina due to the increasing evidence of person-to-person transmission of Andes virus. Several orthohantaviruses were described in the country, but their phylogenetic relationships were inferred from partial genomic sequences. The objectives of this work were to assess the viral diversity of the most prevalent orthohantaviruses associated with HPS cases in the Central-East (CE) region of Argentina, elucidate the geographic patterns of distribution of each variant and reconstruct comprehensive phylogenetic relationships utilizing complete genomic sequencing. To accomplish this, a detailed analysis was conducted of the geographic distribution of reported cases within the most impacted province of the region. A representative sample of cases was then selected to generate a geographic map illustrating the distribution of viral variants. Complete viral genomes were obtained from HPS cases reported in the region, including some from epidemiologically linked cases. The phylogenetic analysis based on complete genomes defined two separate clades in Argentina: Andes virus in the Southwestern region and Andes-like viruses in other parts of the country. In the CE region, Buenos Aires virus and Lechiguanas virus clearly segregate in two subclades. Complete genomes were useful to distinguish person-to-person transmission from environmental co-exposure to rodent population. This study enhances the understanding of the genetic diversity, geographical spread, and transmission dynamics of orthohantaviruses in Central Argentina and prompt to consider the inclusion of Buenos Aires virus and Lechiguanas virus in the species Orthohantavirus andesense, as named viruses.

Summary: On November 2018, a person-to-person transmission outbreak of Andes virus (ANDV) began in the small town of Epuyen, Argentina. The strain involved demonstrated a high capacity for sustained transmission among the human population requiring the implementation of quarantine measures, rigorous contact tracing, isolation of close contacts, and active clinical monitoring to prevent further spread. In this study, we report the isolation of this strain, which we name the ARG-Epuyen after just three passages in cell culture. Complete sequencing revealed only a single amino acid change post-isolation, revealing that it is a non-adapted, wild-type ANDV strain, and its isolation probably represents a critical step toward the development of medical countermeasures against this emerging pathogen. The pathogenicity and transmissibility potential of ARG-Epuyen were evaluated in hamsters, the only animal model for Hantavirus Pulmonary Syndrome. Additionally, this strain was compared with ARG, an ANDV strain previously isolated from the same geographical area in the Argentinian Patagonia, from a rodent specimen. Our findings revealed high infectiousness and efficient hamster-to-hamster transmission through direct contact experiments, although ARG-Epuyen appeared to be less pathogenic than ARG.

Hantavirus Pulmonary Syndrome (HPS), characterized by its high fatality rate, poses a significant public health concern in the Americas. Phylogenetic relationships of orthohantaviruses in the country were inferred from partial genomic sequences. The objectives of this work were to report new complete viral genomes of the known viral variants associated with HPS cases in Central-East region of Argentina, to assess viral diversity, phylogenetic relationships, and to elucidate the geographic patterns of distribution of each variant. To accomplish this, a detailed analysis was conducted of the geographic distribution of reported cases within the most impacted province of the region. The phylogenetic analysis defined clearly separated clades in the country according to their geographic origin. Andes virus (ANDV) segregated from the rest of the sequences, and those representative from the Central East region, Buenos Aires (BAV) and Lechiguanas virus (LECV), were grouped in the same cluster but segregated in two different branches. Importance: In Argentina, most of the HPS cases were associated with ANDV and closely related viruses distributed in four endemic regions. This work focused on obtaining and studying the complete genome of the orthohantaviruses present in the Central East (CE) region (BAV and LECV). Both viruses were responsible for major and minor outbreaks of person- to-person transmission in the country, and the findings may pave the way to study the impact of genetic determinants of viral transmission and to consider the reclassification of the species Orthohantavirus andesense .

Hantavirus Pulmonary Syndrome (HPS) is an emerging infectious disease caused by orthohantaviruses in the Americas. In Argentina, since 1995, several reservoirs and virus variants have been described, but the northeastern and central endemic zones in the country include an area without human or rodent infections, despite sharing rodent species with areas with that disease. The aim of this study was to search for orthohantavirus in rodent communities that inhabit this area, which borders two endemic areas of HPS. Small rodents were captured in June of 2022 through a total effort of 644 trap nights distributed in five grids located in the Iberá National Park, Corrientes, Northeastern Argentina. All rodents were sexed, weighed, and the species was recorded. Blood samples were extracted to detect ANDV‐specific immunoglobulin G (IgG), and to extract the RNA virus. Trimmed sequences were mapped against reference sequences from GenBank. We captured a total of 36 Oligoryzomys flavescens and 15 Oxymycterus rufus. We detected the O. flavescens species infected with Lechiguanas orthohantavirus in the camping area of the National Park. A nucleotide comparison with previously published sequences shows a 98.34% similarity to the virus obtained from a human case of HPS reported in the adjacent Misiones province. This study demonstrated, for the first time, that O. flavescens is a host of the Lechiguanas orthohantavirus in this zone and contributes to closing information gaps on the distribution of orthohantavirus in Argentina. Additionally, the high similarity with the hantavirus found in the human case of Misiones suggests that the reservoir in that province would also be O. flavescens (not previously confirmed). This information permits us to focus on the preventive measurements to protect the human population.

Several orthohantaviruses cause the zoonotic disease hantavirus pulmonary syndrome (HPS) in the Americas. Among them, HPS caused by Andes virus (ANDV) is of great public health concern because it is associated with the highest case fatality rate (up to 50%).

We performed whole-genome sequencing with bait-enrichment techniques to analyze Andes virus (ANDV), a cause of human hantavirus pulmonary syndrome. We used cryopreserved lung tissues from a naturally infected long-tailed colilargo; early, intermediate, and late cell-culture passages of an ANDV isolate from that animal; and lung tissues from golden hamsters experimentally exposed to that ANDV isolate. The resulting complete genome sequences were subjected to detailed comparative genomic analysis against American orthohantaviruses. We identified four amino-acid substitutions related to cell-culture adaptation that resulted in attenuation of ANDV in the typically lethal golden hamster animal model of hantavirus pulmonary syndrome. Mutations in the ANDV nucleocapsid protein, glycoprotein, and small nonstructural protein open reading frames correlated with mutations typical for ANDV strains associated with increased pathogenesis in the small animal model. Finally, we identified three amino-acid substitutions, two in the small nonstructural protein and one in the glycoprotein, that were only present in the clade of viruses associated with person-to-person efficient transmission. Our results indicate that there are virulence-associated and transmission-associated single-nucleotide polymorphisms that could be used to predict strain-specific ANDV virulence and/or transmissibility. Importance Several orthohantaviruses cause the zoonotic disease hantavirus pulmonary syndrome (HPS) in the Americas. Among them, HPS caused by Andes virus (ANDV) is of great public-health concern because it is associated with the highest case-fatality rate (up to 50%). ANDV is also the only orthohantavirus associated with relatively robust evidence of person-to-person transmission. This work reveals nucleotide changes in the ANDV genome that are associated with virulence attenuation in an animal model and increased transmissibility in humans. These findings may pave the way to early severity predictions in future ANDV-caused HPS outbreaks.

Hantavirus Pulmonary Syndrome in a COVID-19 Patient, Argentina, 2020