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We conducted a retrospective phylogenetic analysis of Mayaro virus (MAYV) detected in French Guiana during 1996-2024. Analysis revealed circulation of MAYV genotype D sublineage 2 and suggested introduction from Brazil and spread to Haiti and Venezuela. Phylogenetic findings support endemic circulation and reinforce the need for MAYV surveillance in the region.

As a member of the Alphavirus genus, Getah virus (GETV) has become an emerging pathogen posing severe threats to animal health and public health security. In recent years, GETV has caused increasing outbreaks in swine herds, leading to substantial economic losses in the pig industry in China. Here, we report continuous GETV outbreaks on pig farms across southeastern China between September 2024 and December 2025. A total of 185 clinical samples were examined, among which 27 were positive (14.6%). Subsequently, five GETV strains were successfully isolated and subjected to whole-genome sequencing. Phylogenetic analysis revealed that all the 5 isolated strains belonged to genotype III(GIII), with two strains (GETV-AHX2024 and GETV-JS2024) forming a distinct GIII variant clade. Notably, multiple specific amino acid mutations were identified in the nsp3, C, E2, 6K, and E1 proteins and 3′UTR of these GIII variant strains. Pathogenicity in mice revealed that mice infected with the GIII variant strain GETV-JS2024 exhibited a longer viral shedding period compared with other strains. These findings highlight the emergence of GETV GIII variant strains in southeastern China and suggest their altered pathogenic performance in mice. These results supplied critical data for molecular surveillance and subsequent pathogenic analysis of GETV in China.

Getah virus (GETV) is a mosquito‐borne alphavirus with an expanding host range and an increasing impact on swine production, particularly in neonatal piglets. In this study, a severe disease outbreak characterized by acute diarrhea and high mortality occurred among suckling piglets on a commercial pig farm in central China. Comprehensive pathogen screening excluded common bacterial pathogens and major enteric viruses, whereas GETV RNA was consistently detected in multiple tissues. A GETV strain, designated GETV‐WH, was successfully isolated from lung tissue and propagated in BHK‐21 cells, where it reproducibly induced pronounced cytopathic effects (CPEs). The isolate was confirmed by immunofluorescence assay (IFA) using a GETV E2–specific monoclonal antibody and further purified by plaque assays. Growth kinetics analysis demonstrated efficient viral replication, with peak titers exceeding 10 8 TCID 50 /mL at 24 h postinfection. Experimental infection of 5‐day‐old piglets resulted in rapid disease progression characterized by hypothermia, systemic viral dissemination, severe multiorgan lesions, and 100% mortality within 2 days postinoculation, indicating high virulence of the isolate in neonatal piglets. Complete genome sequencing and comparative analysis identified multiple amino acid substitutions relative to the reference strain MM2021, including two unique substitutions located in NSP1 and the E2 protein. Phylogenetic analysis based on complete genome sequences placed GETV‐WH within genetic Group III, where it formed a distinct branch among contemporary Chinese strains. Collectively, these findings demonstrate that GETV‐WH is a highly pathogenic GETV strain capable of causing acute systemic infection and lethal disease in neonatal piglets, highlighting the potential threat posed by highly virulent GETV variants to swine health.

We detected Mayaro virus (MAYV) in 3.4% (28/822) of febrile patients tested during 2018-2021 from Roraima State, Brazil. We also isolated MAYV strains and confirmed that these cases were caused by genotype D. Improved surveillance is needed to better determine the burden of MAYV in the Amazon Region.

Chikungunya virus (CHIKV) and Mayaro virus (MAYV) are emergent arthropod-borne viruses that produce outbreaks of acute febrile illness with arthropathy. Despite their different continental origins, CHIKV and MAYV are closely related and are components of the Semliki Forest Complex of the Alphavirus (Togaviridae). MAYV and, more recently, CHIKV, which are both transmitted by Aedes mosquitoes, have resulted in severe public health problems in the Americas, including Brazil. In this review, we present aspects of the pathogenesis, clinical presentation and treatment of febrile illnesses produced by CHIKV and MAYV. We also discuss the epidemiological aspects and effects related to the prophylaxis of infections by both viruses.

Mayaro virus (MAYV) is an arbovirus that is endemic to tropical forests in Central and South America, particularly within the Amazon basin. In recent years, concern has increased regarding MAYV’s ability to invade urban areas and cause epidemics across the region. We conducted a systematic literature review to characterise the evolutionary history of MAYV, its transmission potential, and exposure patterns to the virus. We analysed data from the literature on MAYV infection to produce estimates of key epidemiological parameters, including the generation time and the basic reproduction number, R 0 . We also estimated the force-of-infection (FOI) in epidemic and endemic settings. Seventy-six publications met our inclusion criteria. Evidence of MAYV infection in humans, animals, or vectors was reported in 14 Latin American countries. Nine countries reported evidence of acute infection in humans confirmed by viral isolation or reverse transcription-PCR (RT-PCR). We identified at least five MAYV outbreaks. Seroprevalence from population based cross-sectional studies ranged from 21% to 72%. The estimated mean generation time of MAYV was 15.2 days (95% CrI: 11.7–19.8) with a standard deviation of 6.3 days (95% CrI: 4.2–9.5). The per-capita risk of MAYV infection (FOI) ranged between 0.01 and 0.05 per year. The mean R 0 estimates ranged between 2.1 and 2.9 in the Amazon basin areas and between 1.1 and 1.3 in the regions outside of the Amazon basin. Although MAYV has been identified in urban vectors, there is not yet evidence of sustained urban transmission. MAYV’s enzootic cycle could become established in forested areas within cities similar to yellow fever virus.

For 30 years it was thought the alphavirus 6K gene encoded a single 6 kDa protein. However, through a bioinformatics search 10 years ago, it was discovered that there is a frameshifting event and two proteins, 6K and transframe (TF), are translated from the 6K gene. Thus, many functions attributed to the 6K protein needed reevaluation to determine if they properly belong to 6K, TF, or both proteins. In this mini-review, we reevaluate the past research on 6K and put those results in context where there are two proteins, 6K and TF, instead of one. Additionally, we discuss the most cogent outstanding questions for 6K and TF research, including their collective importance in alphavirus budding and their potential importance in disease based on the latest virulence data.

Getah virus (GETV) is a member of the alphavirus genus, and it infects a variety of animal species, including horses, pigs, cattle, and foxes. Human infection with this virus has also been reported. The structure of GETV has not yet been determined. In this study, we report the cryo-EM structure of GETV at a resolution of 3.5 Å. This structure reveals conformational polymorphism of the envelope glycoproteins E1 and E2 at icosahedral 3-fold and quasi-3-fold axes, which is believed to be a necessary organization in forming a curvature surface of virions. In our density map, three extra densities are identified, one of which is believed a “pocket factor”; the other two are located by domain D of E2, and they may maintain the stability of E1/E2 heterodimers. We also identify three N-glycosylations at E1 N141, E2 N200, and E2 N262, which might be associated with receptor binding and membrane fusion. The resolving of the structure of GETV provides new insights into the structure and assembly of alphaviruses and lays a basis for studying the differences of biology and pathogenicity between arthritogenic and encephalitic alphaviruses.

The Mayaro virus (MAYV) is an arbovirus with emerging potential, though with a limited understanding of its epidemiology and evolution due to the lack of studies and surveillance. Here, we investigated 71 MAYV genome sequences from the Americas available at GenBank and characterized the phylogenetic relationship among virus strains. A phylogenetic analysis showed that sequences were grouped according to the genotypes L, D, and N. Genotype D sequences were closely related to sequences collected in adjacent years and from their respective countries, suggesting that isolates may have originated from circulating lineages. The coalescent analysis demonstrated similar results, indicating the continuous circulation of the virus between countries as well. An unidentified sequence from the USA was grouped with genotype D, suggesting the insertion of this genotype in the country. Furthermore, the recombination analysis detected homologous and three heterologous hybrids which presented an insertion into the nsP3 protein. Amino acid substitutions among sequences indicated selective pressure sites, suggesting viral adaptability. This also impacted the binding affinity between the E1–E2 protein complex and the Mxra8 receptor, associated with MAYV entry into human cells. These results provide information for a better understanding of genotypes circulating in the Americas.

Babanki virus is a subtype of the Sindbis virus, a widespread arthropod-borne alphavirus circulating in Eurasia, Africa, and Oceania. Characterized by rashes and arthritis, clinical infections due to Sindbis were mainly reported in Africa, Australia, Asia, and Europe. However, its sub-type, Babanki virus, was reported in Northern Europe and Africa, where its epidemiology potential remains poorly understood. The diagnosis of alphaviruses is mainly based on serological testing and conventional PCR methods, which have considerable limits. In this study, we developed a real-time qRT-PCR assay for the detection of Babanki virus. The analytical sensitivity and specificity of the newly established assay were evaluated using in vitro standard RNA and related viruses relevant to the African context, respectively. In addition, its diagnostic sensitivity was assessed using a subset of Babanki virus-positive and -negative mosquito pools collected from the field. The new real-time qRT-PCR assay exhibited a 100% specificity, a 95% detection limit of 1 RNA molecule/reaction, and a diagnostic sensitivity of up to 120 pfu/reaction. This newly established assay could be useful not only for the detection of Babanki virus during epidemics but also in future experimental and surveillance studies focusing on their epidemiology and pathogenicity.