Yellow fever (YF) is a re-emerging viral zoonosis caused by the Yellow Fever virus (YFV), affecting humans and non-human primates (NHP). YF is endemic in South America and Africa, being considered a burden for public health worldwide despite the availability of an effective vaccine. Acute infectious disease can progress to severe hemorrhagic conditions and has high rates of morbidity and mortality in endemic countries. In 2016, Brazil started experiencing one of the most significant YF epidemics in its history, with lots of deaths being reported in regions that were previously considered free of the disease. Here, we reviewed the historical aspects of YF in Brazil, the epidemiology of the disease, the challenges that remain in Brazil’s public health context, the main lessons learned from the recent outbreaks, and our perspective for facing future YF epidemics.

Yellow fever (YF) disease is a viral infection caused by Orthoflavivirus flavi (YFV). YFV is transmitted by hematophagous daytime-biting mosquitoes, predominantly Haemagogus spp. and Sabethes spp. in the sylvatic cycles, and Aedes spp. in urban cycles. In this work, we correlated vaccination coverage with the occurrence and spread of the disease throughout Brazil during the years 2016–2018. The Vale do Mucuri and Vale do Rio Doce regions in Minas Gerais state had the highest number of reported cases. Despite being considered areas with vaccine recommendation since 2008, these regions had less than 60% and 70% vaccination coverage in 2016. The outbreak of YF in Brazil has shown that surveillance for emerging diseases should be constant, especially in relation to the national immunization program. In this study, we observed that low vaccination coverage and the lack of public policies aimed at this region with low population development may have an impact on the reemergence of YF.

Dengue and obesity are currently highly prevalent conditions worldwide and the association between these two conditions may result in greater risk for DENV infection and disease severity. In this study the association between obesity and recent, inapparent dengue was investigated. Serum DENV IgM and NS1 were evaluated in 49 adult volunteers (15 lean and 34 individuals with obesity, according to body mass index), between September 2017 and June 2018. Adiposity, endocrine, metabolic, and immune data of the participants were also obtained. None of the study participants tested positive for the DENV NS1 antigen. DENV IgM was detected in 33.3% of the lean individuals, and in 44.1% of those with obesity; the presence of DENV IgM was not associated with body mass index (OR = 1.32, 95% CI = 0.59–2.98, p = 0.48). However, body fat index was higher in obese individuals who had recent inapparent dengue (14.7 ± 3.1 versus 12.7 ± 2.1 kg/m², p = 0.04), as was the expression of CD11b by classical (CD14⁺⁺CD16⁻) monocytes (1103.0 ± 311.3 versus 720.3 ± 281.1 mean fluoresce intensity). Our findings suggest an association between adiposity and recent inapparent dengue and the involvement of classical monocytes in this association.

Long-term neurofunctional outcomes after pediatric SARS-CoV-2 infection remain incompletely understood, particularly in relation to acute antiviral immune responses. This exploratory observational pilot study assessed neurofunctional performance approximately six months after infection and its association with acute nasopharyngeal interferon-related gene expression. Sixteen children aged 3–10 years with RT-qPCR-confirmed mild COVID-19 underwent cognitive, gross motor, and functional exercise assessments. Transcript abundance of IFNA2, IFNB1, IFNL2/3, IFI6, and OAS2 was evaluated by qPCR. Five children (31.25%) scored below the age-specific MMSE cutoff, and five of 14 children (35.71%) had below-average TGMD-2 performance. Thirteen completed the ISWT, achieving 53.95 ± 13.55% of the individually predicted distance. IFNB1, IFI6, and OAS2 were detected in all acute-phase samples, whereas IFNA2 and IFNL2/3 were not detected. No statistically significant associations were identified between the detected transcripts and subsequent neurofunctional outcomes. Although the small sample size, absence of pre-infection assessments, and lack of an uninfected comparison group limit interpretation of the findings, this pilot study provides preliminary descriptive data integrating acute mucosal interferon-related gene expression with subsequent neurofunctional assessments in children, supporting further investigation in larger, controlled cohorts.