The Risk of Virus Emergence in South America: A Subtle Balance Between Increasingly Favorable Conditions and a Protective Environment.

South American ecosystems host astonishing biodiversity, with potentially great richness in viruses. However, these ecosystems have not yet been the source of any widespread, epidemic viruses. Here we explore a set of putative causes that may explain this apparent paradox. We discuss that human presence in South America is recent, beginning around 14,000 years ago; that few domestications of native species have occurred; and that successive immigration events associated with Old World virus introductions reduced the likelihood of spillovers and adaptation of local viruses into humans. Also, the diversity and ecological characteristics of vertebrate hosts might serve as protective factors. Moreover, although forest areas remained well preserved until recently, current brutal, sudden, and large-scale clear cuts through the forest have resulted in nearly no ecotones, which are essential for creating an adaptive gradient of microbes, hosts, and vectors. This may be temporarily preventing virus emergence. Nevertheless, the mid-term effect of such drastic changes in habitats and landscapes, coupled with explosive urbanization and climate changes, must not be overlooked by health authorities.

Seroconversion of rheumatoid arthritis patients after yellow fever vaccination.

Vaccination is a current strategy used to prevent infections in patients with immune-mediated rheumatic diseases. However, the use of live-attenuated vaccines prepared from living microorganisms in these patients should be avoided due to the risk of acquiring infections. The present study aimed to investigate the effect of the yellow fever (YF) vaccine (a live-attenuated vaccine) in 12 patients with rheumatoid arthritis (RA). The sample comprised 12 patients (9 females and 3 males; mean age 52.2 ± 6.5 years) with RA, who inadvertently received fractionated 17D yellow fever vaccination during an outbreak of this disease. In this cohort, 10 were administered leflunomide; 7 were administered methotrexate; 6 were administered prednisone (median dose of 5.0 mg/day); 6 took biologic drugs; and 1 took tofacitinib. All but one patient (used rituximab, prednisone, and methotrexate) seroconverted. None of them developed clinical signs of infection after the procedure. The fractionated dose of the YF vaccine is effective and safe in the observed sample. Key Points • Patients with autoimmune inflammatory rheumatic diseases (AIIRD) are at a high risk of acquiring infections • The fractionated dose of the YF vaccine is effective and safe in the observed sample • Vaccination against YF should be avoided in patients with AIIRD under immunosuppression owing to the risks of inducing YF infection.

Zika virus - an overview.

Zika virus (ZIKV) is currently one of the most important emerging viruses in the world. Recently, it has caused outbreaks and epidemics, and has been associated with severe clinical manifestations and congenital malformations. However to date, little is known about the pathogenicity of the virus and the consequences of ZIKV infection. In this paper, we provide an overview of the current knowledge on ZIKV.

First evidence of asymptomatic infection related to the Araucaria (Juquitiba-like) hantavirus.

Hantavirus pulmonary syndrome (HPS) is a severe disease, transmitted to humans by inhalation of virus-contaminated aerosols from rodent excreta. Epidemiological, clinical and laboratory data confirmed a fatal HPS case and an asymptomatic infection in a household contact, both caused by Araucaria hantavirus, which has previously been found only in patients with HPS. This is the first report of asymptomatic infection related to a pathogenic hantavirus genotype, highlighting the need for additional studies on characterisation of viral and genetic mechanisms associated with this disease.

Evidence of circulation of Laguna Negra-like hantavirus in the Central West of Brazil: case report.

BACKGROUND: Hantavirus pulmonary syndrome has been reported with increasing frequency in some Brazilian regions, but information about viral genetic identification is still limited. Recently, the state of Mato Grosso, in the Legal Amazon of Brazil, experienced a growing number of hantavirus pulmonary syndrome (HPS) cases but the genetic characterization of the causative hantavirus is still missing. OBJECTIVES: Our goal was to identify the hantavirus strain involved in a fatal HPS case in the Central region of Brazil. STUDY DESIGN: Nested RT-PCR was conducted on blood clot samples from an HPS patient from Mato Grosso. PCR-positive samples were sequenced, and the resulting sequences were compared with reference samples. Viral antigens were detected by immunohistological analyses in lung and liver tissues. RESULTS: Analyses of the viral RNA isolated from the patient identified a Laguna Negra (LN)-like virus as the causative agent and histological analysis of lung sections were compatible with the genetic characterization. CONCLUSIONS: This is the first report of circulation and human infection by a Laguna Negra-like hantavirus in Brazil.

Dengue virus infections: comparison of methods for diagnosing the acute disease.

BACKGROUND: The control of dengue depends solely on the control of the insect vector and efficient diagnosis of human cases as no vaccines or specific treatments are currently available. Existing diagnostic methods for suspected clinical cases are complicated by the short duration of viraemia and by serological cross-reactivity with epitopes from other flaviviruses. OBJECTIVES: To evaluate PCR-based tests (nested reverse transcription (RT)-PCR and real-time RT-PCR) for the detection and serotyping of dengue virus and compare the results with those obtained with a widely used immunological test (IgM antibody capture ELISA-MAC-ELISA). RESULTS AND CONCLUSIONS: The PCR-based methods were more effective in the first few days of infection, whereas the MAC-ELISA became more sensitive 5 or 6 days after disease onset. These results suggest that the best method for dengue diagnosis is a combination of PCR-based and immunological tests. Real-time RT-PCR was more sensitive than the nested RT-PCR approach. Furthermore, it was rapid, reproducible and highly specific, making it a potential method for the diagnosis of dengue fever.

Genome analysis of dengue type-1 virus isolated between 1990 and 2001 in Brazil reveals a remarkable conservation of the structural proteins but amino acid differences in the non-structural proteins.

We have investigated the genetic diversity of dengue type-1 (DEN-1) virus in Brazil. The full nucleotide sequences of three DEN-1 virus isolated from DEN fever (DF) and DEN hemorrhagic fever patients in northeastern Brazil in 1997 (BR/97) and one from a DF patient in the south of Brazil in 2001 (BR/01) were compared to that of the reference strain BR/90 obtained in the city of Rio de Janeiro in 1990. Sequence analysis showed that the structural proteins were remarkably conserved between all isolates. A total of 27 amino acid changes occurred throughout the non-structural proteins. Among them, nine amino acid substitutions were specific of BR/97 and BR/01 isolates, indicating that in situ evolution of these strains had occurred. Within the BR/97 and BR/01 samples, some amino acid substitutions have been previously identified in DEN-1 virus strains sequenced so far, suggesting that recombination events might have occurred.