Little-known virus is on the rise in South America.

Deforestation and climate change may be helping Oropouche virus spread far beyond the Amazon Basin.

Molecular Epidemiology of Mayaro Virus among Febrile Patients, Roraima State, Brazil, 2018-2021.

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.

Detection and genetic diversity of Mopeia virus in Mastomys natalensis from different habitats in the Limpopo National Park, Mozambique.

Mammarenaviruses have been a growing concern for public health in Africa since the 1970s when Lassa virus cases in humans were first described in west Africa. In southern Africa, a single outbreak of Lujo virus was reported to date in South Africa in 2008 with a case fatality rate of 80%. The natural reservoir of Lassa virus is Mastomys natalensis while for the Lujo virus the natural host has yet to be identified. Mopeia virus was described for the first time in M. natalensis in the central Mozambique in 1977 but few studies have been conducted in the region. In this study, rodents were trapped between March and November 2019in villages, croplands fields and mopane woodland forest. The aim was to assess the potential circulation and to evaluate the genetic diversity of mammarenaviruses in M. natalensis trapped in the Limpopo National Park and its buffer zone in Massingir district, Mozambique. A total of 534 M. natalensis were screened by RT-PCR and the overall proportion of positive individuals was 16.9%. No significant differences were detected between the sampled habitats (χ2 = 0.018; DF = 1; p = 0.893). The Mopeia virus (bootstrap value 91%) was the Mammarenavirus circulating in the study area sites, forming a specific sub-clade with eight different sub-clusters. We concluded that Mopeia virus circulates in all habitats investigated and it forms a different sub-clade to the one reported in central Mozambique in 1977.

A Retrospective Survey of Rodent-borne Viruses in Rural Populations of Brazilian Amazon.

INTRODUCTION: The Amazon tropical rainforest has the most dense and diverse ecosystem worldwide. A few studies have addressed rodent-borne diseases as potential hazards to humans in this region. METHODS: A retrospective survey was conducted using enzyme-linked immunosorbent assay for detecting mammarenavirus and orthohantavirus antibodies in 206 samples collected from rural settlers of the Brazilian Western Amazonian region. RESULTS: Six (2.91%) individuals in the age group of 16 to 36 years were found to possess antibodies against mammarenavirus. CONCLUSION: Evidence of previous exposure to mammarenavirus in the rural population points to its silent circulation in this region.

Arenavirus as a potential etiological agent of odontogenic tumours in humans.

Odontogenic tumors (OT) are considered rare events and their epidemiologic data are scarce and under-estimated in developing countries because there is no systematic collection of clinical features including histological analyses of the tissue samples. Furthermore, there is an underestimation of the disease relevance and affected people are often marginalized in spite of severe functional impairment of aero-digestive tract. Etiology of OT in humans is still unknown and it represents an important therapeutic and diagnostic challenge.Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of the arenavirus family of viruses. The disease is endemic in the rodent population in West-East Africa. Humans usually become infected with Lassa virus through exposure to the food or household items contaminated with urine or feces of infected rats. It is also reported person-to-person infections. About 80% of people infected by Lassa virus have no symptoms but the virus establishes a life-long persistent infection.The present commentary significance is to start, for the first time ever, a systematic collection of clinical features and tissue sample collection at the St. Mary's Hospital in Lacor (Gulu) North Uganda where the considered pathologies have an important frequency. The systematic collection will allow to corroborate the possible association between arenaviruses infection and pathogenesis of odontogenic tumors in humans.

Density dependence and persistence of Morogoro arenavirus transmission in a fluctuating population of its reservoir host.

A key aim in wildlife disease ecology is to understand how host and parasite characteristics influence parasite transmission and persistence. Variation in host population density can have strong impacts on transmission and outbreaks, and theory predicts particular transmission-density patterns depending on how parasites are transmitted between individuals. Here, we present the results of a study on the dynamics of Morogoro arenavirus in a population of multimammate mice (Mastomys natalensis). This widespread African rodent, which is also the reservoir host of Lassa arenavirus in West Africa, is known for its strong seasonal density fluctuations driven by food availability. We investigated to what degree virus transmission changes with host population density and how the virus might be able to persist during periods of low host density. A seven-year capture-mark-recapture study was conducted in Tanzania where rodents were trapped monthly and screened for the presence of antibodies against Morogoro virus. Observed seasonal seroprevalence patterns were compared with those generated by mathematical transmission models to test different hypotheses regarding the degree of density dependence and the role of chronically infected individuals. We observed that Morogoro virus seroprevalence correlates positively with host density with a lag of 1-4 months. Model results suggest that the observed seasonal seroprevalence dynamics can be best explained by a combination of vertical and horizontal transmission and that a small number of animals need to be infected chronically to ensure viral persistence. Transmission dynamics and viral persistence were best explained by the existence of both acutely and chronically infected individuals and by seasonally changing transmission rates. Due to the presence of chronically infected rodents, rodent control is unlikely to be a feasible approach for eliminating arenaviruses such as Lassa virus from Mastomys populations.

A Retrospective Survey of Rodent-borne Viruses in Rural Populations of Brazilian Amazon

Abstract INTRODUCTION: The Amazon tropical rainforest has the most dense and diverse ecosystem worldwide. A few studies have addressed rodent-borne diseases as potential hazards to humans in this region. METHODS: A retrospective survey was conducted using enzyme-linked immunosorbent assay for detecting mammarenavirus and orthohantavirus antibodies in 206 samples collected from rural settlers of the Brazilian Western Amazonian region. RESULTS: Six (2.91%) individuals in the age group of 16 to 36 years were found to possess antibodies against mammarenavirus. CONCLUSION: Evidence of previous exposure to mammarenavirus in the rural population points to its silent circulation in this region.

Seroprevalence of arenavirus and hantavirus in indigenous populations from the Caribbean, Colombia

Abstract INTRODUCTION: In Colombia, there is insufficient epidemiological surveillance of zoonotic hemorrhagic viruses. METHODS: We performed a sero-epidemiological study in indigenous populations of Wayuü, Kankuamos, and Tuchin communities using Maciel hantavirus and Junin arenavirus antigens for IgG detection by ELISA. RESULTS IgG antibodies to hantavirus and arenavirus were found in 5/506 (1%) and 2/506 (0.4%) serum samples, respectively. CONCLUSIONS: Arenavirus and hantavirus circulate in indigenous populations from the Colombian Caribbean region, and the results indicate that the indigenous populations are exposed to these zoonotic agents, with unknown consequences on their health, despite low seroprevalence.

Seroprevalence of arenavirus and hantavirus in indigenous populations from the Caribbean, Colombia.

INTRODUCTION: In Colombia, there is insufficient epidemiological surveillance of zoonotic hemorrhagic viruses. METHODS: We performed a sero-epidemiological study in indigenous populations of Wayuü, Kankuamos, and Tuchin communities using Maciel hantavirus and Junin arenavirus antigens for IgG detection by ELISA. RESULTS: IgG antibodies to hantavirus and arenavirus were found in 5/506 (1%) and 2/506 (0.4%) serum samples, respectively. CONCLUSIONS: Arenavirus and hantavirus circulate in indigenous populations from the Colombian Caribbean region, and the results indicate that the indigenous populations are exposed to these zoonotic agents, with unknown consequences on their health, despite low seroprevalence.

Seroprevalence of rodent-borne viruses in Afro-descendent communities in Brazil.

During the Brazilian slavery period, many African migrants were brought to the American continent. Historically, some of these migrants escaped from the Brazilian gold mines and farms to which they had been brought and settled in remote valleys and this was the main mode of resistance to the slavery system. These runaway-slave descendant communities are called quilombos, a group with distinct ethnic identity, specific behavioral habits, including geographic isolation and conservative practices. The objective of this study was to investigate the prevalence of rodent-borne viruses in two Afro-descendent communities from Mato Grosso do Sul State, Midwestern Brazil. A total of 319 individuals from rural and urban quilombola communities were enrolled. Twelve (3.76%) had anti-rodent-borne virus IgG antibodies. Seven (2.19%) were anti-mammarenavirus reactive and nine (2.82%) had anti-orthohantavirus antibodies. The literature includes limited data on the health status of quilombola communities, but all the studies emphasize the disparity of attention of local healthcare personnel to these communities compared to the general population. The findings of this study highlight the vulnerability and the precarious health conditions of quilombola groups, especially those living in rural areas and thus, point to the need of preventive measures to improve access to healthcare for this ethnic group.

Hemorrhagic Fever-Causing Arenaviruses: Lethal Pathogens and Potent Immune Suppressors.

Hemorrhagic fevers (HF) resulting from pathogenic arenaviral infections have traditionally been neglected as tropical diseases primarily affecting African and South American regions. There are currently no FDA-approved vaccines for arenaviruses, and treatments have been limited to supportive therapy and use of non-specific nucleoside analogs, such as Ribavirin. Outbreaks of arenaviral infections have been limited to certain geographic areas that are endemic but known cases of exportation of arenaviruses from endemic regions and socioeconomic challenges for local control of rodent reservoirs raise serious concerns about the potential for larger outbreaks in the future. This review synthesizes current knowledge about arenaviral evolution, ecology, transmission patterns, life cycle, modulation of host immunity, disease pathogenesis, as well as discusses recent development of preventative and therapeutic pursuits against this group of deadly viral pathogens.

Reptarenaviruses in apparently healthy snakes in an Australian zoological collection.

BACKGROUND: Inclusion body disease (IBD) is a disease of snakes with a global distribution and has recently been shown to be caused by reptarenaviruses. Testing for this group of viruses in asymptomatic snakes allows the association between infection and disease to be further elucidated. METHODS: A reptarenavirus was detected by RT-PCR in a reticulated python (Malayopython reticulatus) from an Australian zoological collection that was open-mouth breathing and had erythematous oral mucosa. Another 27 pythons, 4 elapids, 2 colubrids and 2 boas from this collection were then screened. From these animals, swabs, whole blood and/or tissue were tested for reptarenaviruses by RT-PCR. Additionally, blood films from 10 snakes were examined by light microscopy for the presence of inclusion bodies. The majority of samples were collected over a 484-day period. RESULTS: A total of 8 animals were RT-PCR-positive (8/36 = 22.2%): 6 were pythons, 1 was a corn snake (Pantherophis guttatus) and 1 was a Madagascar tree boa (Sanzinia madagascariensis). From them, 57 samples were collected, but only one from each animal was RT-PCR-positive (8/57 = 14.0%). From all 36 animals in this study, 8/182 samples were RT-PCR-positive (4.4%). Inclusion bodies were not recognised in any of the blood films. Only the reticulated python showed signs of illness, which improved without any further intervention. All other RT-PCR-positive snakes were apparently healthy throughout the duration of the study. CONCLUSION: This study showed a weak association between the presence of reptarenaviruses and disease. Testing serially collected swab and whole-blood samples increased the number of animals in which reptarenaviruses were detected.

Rodent-borne viruses survey in rural settlers from Central Brazil

Anthropogenic environmental changes arising from settlement and agriculture include deforestation and replacement of natural vegetation by crops providing opportunities for pathogen spillover from animals to humans. This study aimed to investigate the prevalence of rodent-borne virus infections in seven rural settlements from Midwestern Brazil. Of the 466 individuals tested 12 (2.57%) were reactive for orthohantavirus and 3 (0.64%) for mammarenavirus. These rural settlers lived under unfavorable infrastructure, socioeconomic disadvantages, and unsanitary conditions, representing a risk for rodent-borne infections. Development of public policies towards the improvement of health, sanitation and awareness of rodent-borne diseases in improvised camps and settlements is imperative, in order to reduce morbidity and mortality caused by these diseases.

Rodent-borne viruses survey in rural settlers from Central Brazil.

Anthropogenic environmental changes arising from settlement and agriculture include deforestation and replacement of natural vegetation by crops providing opportunities for pathogen spillover from animals to humans. This study aimed to investigate the prevalence of rodent-borne virus infections in seven rural settlements from Midwestern Brazil. Of the 466 individuals tested 12 (2.57%) were reactive for orthohantavirus and 3 (0.64%) for mammarenavirus. These rural settlers lived under unfavorable infrastructure, socioeconomic disadvantages, and unsanitary conditions, representing a risk for rodent-borne infections. Development of public policies towards the improvement of health, sanitation and awareness of rodent-borne diseases in improvised camps and settlements is imperative, in order to reduce morbidity and mortality caused by these diseases.

Xapuri virus, a novel mammarenavirus: natural reassortment and increased diversity between New World viruses.

Mammarenavirus RNA was detected in Musser's bristly mouse (Neacomys musseri) from the Amazon region, and this detection indicated that rodents were infected with a novel mammarenavirus, with the proposed name Xapuri virus (XAPV), which is phylogenetically related to New World Clade B and Clade C viruses. XAPV may represent the first natural reassortment of the Arenaviridae family and a new unrecognized clade within the Tacaribe serocomplex group.

Widespread arenavirus occurrence and seroprevalence in small mammals, Nigeria.

BACKGROUND: Lassa fever, killing thousands of people annually, is the most reported viral zoonotic disease in Nigeria. Recently, different rodent species carrying diverse lineages of the Lassa virus (LASV) in addition to a novel Mobala-like genetic sequence were detected within the country. Here, screening 906 small mammal specimens from 11 localities for IgG antibodies and incorporating previous PCR detection data involving the same populations, we further describe arenavirus prevalence across Nigeria in relation to host species and geographical location. METHODS: Small mammals were trapped during the period 2011-2015 according to geographical location (endemic and non-endemic zones for Lassa fever), season (rainy and dry seasons between 2011 and 2012 for certain localities) and habitat (indoors, peridomestic settings and sylvatic vegetation). Identification of animal specimens from genera such as Mastomys and Mus (Nannomys) was assisted by DNA sequencing. Small mammals were tested for LASV IgG antibody using an indirect immunofluorescence assay (IFA). RESULTS: Small mammals were infected in both the endemic and non-endemic zones for Lassa fever, with a wider range of species IgG-positive (n = 8) than those which had been previously detected to be PCR-positive (n = 3). IgG-positive species, according to number of infected individuals, were Mastomys natalensis (n = 40), Mastomys erythroleucus (n = 15), Praomys daltoni (n = 6), Mus baoulei (n = 5), Rattus rattus (n = 2), Crocidura spp. (n = 2), Mus minutoides (n = 1) and Praomys misonnei (n = 1). Multimammate mice (Mastomys natalensis and M. erythroleucus) were the most ubiquitously infected, with animals testing positive by either PCR or IgG in 7 out of the 11 localities sampled. IgG prevalence in M. natalensis ranged from 1% in Abagboro, 17-36 % in Eguare Egoro, Ekpoma and Ngel Nyaki, up to 52 % in Mayo Ranewo. Prevalence according to locality, season and age was not, however, statistically significant for M. natalensis in Eguare Egoro and Ekpoma, localities that were sampled longitudinally. CONCLUSIONS: Overall, our study demonstrates that arenavirus occurrence is probably more widely distributed geographically and in extent of host taxa than is currently realized. This expanded scope should be taken into consideration in Lassa fever control efforts. Further sampling should also be carried out to isolate and characterize potential arenaviruses present in small mammal populations we found to be seropositive.

[Arenavirus research and antiviral candidate].

Arenavirus is a genetic term for viruses belonging to the family Arenaviridae and is presented from lymphocytic choriomeningitis virus (LCMV), which shows almost no pathogenicity to humans, to Lassa virus, Junin virus, Machupo virus, Chapare virus, Lujo virus, Sabia virus, and Guanarito virus, which shows high pathogenicity to humans. These viruses except for LCMV are risk group 4 pathogens specified by World Health Organization. Based on this designation, it is designated as Class I pathogens in Japan. Although there have been no reports excluding one imported case of the Lassa fever patient, it is not surprising whenever imported cases occur in our country. Considering the disease severity and mortality rate, it is an urgent matter to develop vaccines and therapeutic drugs in endemic areas, and maintenances of these are also important in countries other than endemic areas. However, basic research on highly pathogenic arenavirus infections and development of therapeutic drugs are not easily progressed, because handling in highly safe research facilities is indispensable. In this article, we will outline the current knowledge from the recent basic research on arenavirus to the development situation of antivirals against arenaviruses.