Oropouche virus as an emerging cause of acute febrile illness in Colombia

Arbovirus infections are frequent causes of acute febrile illness (AFI) in tropical countries. We conducted health facility-based AFI surveillance at four sites in Colombia (Cucuta, Cali, Villavicencio, Leticia) during 2019-2022. Demographic, clinical and risk factor data were collected from persons with AFI that consented to participate in the study (n = 2,967). Serologic specimens were obtained and tested for multiple pathogens by RT-PCR and rapid test (Antigen/IgM), with 20.7% identified as dengue positive from combined testing. Oropouche virus (OROV) was initially detected in serum by metagenomic next-generation sequencing (mNGS) and virus target capture in a patient from Cúcuta. Three additional infections from Leticia were confirmed by conventional PCR, sequenced, and isolated in tissue culture. Phylogenetic analysis determined there have been at least two independent OROV introductions into Colombia. To assess OROV spread, a RT-qPCR dual-target assay was developed which identified 87/791 (10.9%) viremic cases in AFI specimens from Cali (3/53), Cucuta (3/19), Villavicencio (38/566), and Leticia (43/153). In parallel, an automated anti-nucleocapsid antibody assay detected IgM in 27/503 (5.4%) and IgG in 92/568 (16.2%) patients screened, for which 24/68 (35.3%) of PCR positives had antibodies. Dengue was found primarily in people aged <18 years and linked to several clinical manifestations (weakness, skin rash and petechiae), whereas Oropouche cases were associated with the location, climate phase, and odynophagia symptom. Our results confirm OROV as an emerging pathogen and recommend increased surveillance to determine its burden as a cause of AFI in Colombia.

Characterization of Dengue Virus Serotype 2 Cosmopolitan Genotype Circulating in Colombia

Dengue virus (DENV) is the etiological agent of dengue fever (DF), which is among the most prevalent vector-borne diseases in the tropics. In 2022, the Colombian health surveillance system reported more than 69,000 cases of DF. As part of a hospital-based fever surveillance study, acute-phase sera were collected from 4,545 patients with suspected dengue between 2020 and 2023 in three municipalities of Colombia. Combined reverse transcription-polymerase chain reaction and antigen rapid testing confirmed that 376 patients (8.3%) had DF. The virus was isolated in cell culture from 166 of these patients (44.1%), and genome sequencing was performed successfully on 122 (73.5%). Three DENV serotypes (1, 2, and 3) were identified. Phylogenetic analyses of the DENV-2 sequences revealed that 42 of 50 of the isolates (84%) belonged to the DENV-2 cosmopolitan genotype lineage, clustering with sequences from Asia, Peru, and Brazil. We report the detection, isolation, and whole-genome sequencing (11 Kb) of the DENV-2 cosmopolitan genotype and its recent introduction to Colombia.

Emergence, persistence, and positive selection of yellow fever virus in Colombia

Yellow fever virus (YFV) is an arbovirus that causes acute febrile illness (AFI), in tropical areas of South America and Africa. Through a 2020-2023 AFI study in Leticia, Colombia, leveraging metagenomic next-generation sequencing (mNGS), we identified and isolated YFV (LET1450). Phylogenetic analysis showed this strain belongs to South American genotype II (SamII), linked to Peruvian and Bolivian sequences emerging around 1989. Phylodynamic analysis indicates these strains, with a unique genetic makeup, could have reduced vaccine susceptibility, and due to positive Darwinian selection have an enhanced adaptive capacity. Antigenic analysis identified additional immune-evasive traits and this strain's potential for wider Latin American spread. Phylogeographic reconstruction demonstrated the persistence of YFV in Colombia is not due to repeated external introductions, but results from continuous, cryptic internal circulation. This study highlights the crucial role of mNGS in monitoring emerging strains and underscores the need for genomic surveillance of YFV and other arboviral infections.

Mayaro Virus as the cause of Acute Febrile Illness in the Colombian Amazon Basin

Introduction

Mayaro Fever (MF) is a tropical disease caused by the Mayaro virus (MAYV), with outbreaks documented in Latin America.

Methods

A hospital-based fever surveillance in Leticia, Colombian Amazon, collected sera from 1,460 patients aged 5-89 between December 2020 and April 2023.

Results

Dengue and malaria were the main diagnoses (19.4 and 5.8%, respectively), leaving 71.4% of cases unidentified after testing. Metagenomic sequencing and real-time RT-qPCR testing identified MAYV in two patients (25-year-old male and an 80-year-old female) exhibiting typical symptoms, of MF including rash, joint pain, and fever. Phylogenetics analysis of these two viruses revealed a close relationship to Peruvian strains within the MAYV D genotype.

Discussion

The study of AFI in Leticia, Colombia, identified dengue as prevalent, with malaria, COVID-19, Influenza, and Zika viruses also detected. Despite extensive testing, most cases remained unexplained until metagenomic sequencing revealed MAYV, previously unseen in Colombia but known in neighboring countries.

Conclusion

This study presents the first near full-length genomes of MAYV in Colombia, highlighting the need for further seroprevalence studies and enhanced surveillance to understand and control the spread of the virus in the region.

Co-Circulation of 2 Oropouche Virus Lineages, Amazon Basin, Colombia, 2024

In early 2024, explosive outbreaks of Oropouche virus (OROV) linked to a novel lineage were documented in the Amazon Region of Brazil. We report the introduction of this lineage into Colombia and its co-circulation with another OROV lineage. Continued surveillance is needed to prevent further spread of OROV in the Americas.

Protocol for detection of Oropouche viruses from human serum

Oropouche virus (OROV), an arthropod-borne virus, has reemerged in the Americas. In 2023-2024, the largest quantitative reverse-transcription PCR (RT-qPCR)-confirmed outbreak of OROV was reported and was associated with severe clinical outcomes for the first time. Moreover, a dramatic increase in cases is unfolding in early 2025. Here, we provide a protocol for detecting OROV from human serum. We describe steps for viral isolation, titration, and an in-house RT-qPCR validated in the field. We then detail procedures for measurement of anti-OROV-neutralizing antibodies. For complete details on the use and execution of this protocol, please refer to Ciuoderis et al.1 and Usuga et al.2.