Approaches to produce and characterize recombinant protein VP1-2A of HAV for serological rapid test application.

Studies reporting the expression of hepatitis A virus (HAV) structural proteins, specifically recombinant VP1-2A containing an immunogenic activity, use the Escherichia coli system. Recombinant HAV proteins may represent a source of less expensive antigens for application in different diagnostic platforms. However, the formation of insoluble aggregates is an obstacle to obtaining large amounts of HAV proteins in their native form. To overcome this obstacle, some approaches were applied in this study to improve purification, solubility, and protein expression levels. Critical properties were evaluated. The introduction of another insertion codon to increase the protein concentration and vector activity was observed and verified by SDS-PAGE. The expression was established with 0.4 mM IPTG for 4 h at 37 °C. The VP1 protein was partially soluble at an isoeletric point (pI) of 6.45. The majority of HAV VP1-2A proteins measured 45.19 kDa in size and had a homogeneity of 53.58%. Multi-antigen print immunoassay (MAPIA) showed antigenicity at different HAV VP1-2A concentrations, and microsphere-based immunoassays showed a specificity of 100% and a sensitivity of 84%. HAV VP1-2A was characterized using different sensitivity methods to prove its biological activity, indicating its use as a tool for the diagnosis of Hepatitis A virus infection.

Higher frequency of Human herpesvirus-6 (HHV-6) viral DNA simultaneously with low frequency of Epstein-Barr virus (EBV) viral DNA in a cohort of multiple sclerosis patients from Rio de Janeiro, Brazil.

Multiple sclerosis (MS) is a chronic neuroinflammatory and neurodegenerative disease of the central nervous system (CNS). The etiology of MS is not well understood, but it's likely one of the genetic and environmental factors. Approximately 85% of patients have relapsing-remitting MS (RRMS), while 10-15% have primary progressive MS (PPMS). Epstein-Barr virus (EBV) and Human herpesvirus 6 (HHV-6), members of the human Herpesviridae family, are strong candidates for representing the macroenvironmental factors associated with MS) pathogenesis. Antigenic mimicry of EBV involving B-cells has been implicate in MS risk factors and concomitance of EBV and HHV-6 latent infection has been associated to inflammatory MS cascade. To verify the possible role of EBV and HHV-6 as triggering or aggravating factors in RRMS and PPMS, we compare their frequency in blood samples collected from 166 MS patients. The presence of herpes DNA was searched by real-time PCR (qPCR). The frequency of EBV and HHV-6 in MS patients were 1.8% (3/166) and 8.9% (14/166), respectively. Among the positive patients, 100% (3/3) EBV and 85.8% (12/14) HHV-6 are RRMS and 14.4% (2/14) HHV-6 are PPMS. Detection of EBV was 1.2% (2/166) and HHV-6 was 0.6% (1/166) in blood donors. About clinical phenotype of these patients, incomplete multifocal myelitis, and optic neuritis were the main CNS manifestations. These are the first data about concomitant infection of these viruses in MS patients from Brazil. Up to date, our findings confirm a higher prevalence in female with MS and a high frequency of EBV and HHV-6 in RRMS patients.

Presence and clinical impact of human herpesvirus-6 infection in patients with moderate to critical coronavirus disease-19.

Human herpesvirus-6 (HHV-6) may cause serious diseases in immunocompromised individuals. SARS-CoV-2/HHV-6 coinfection has been emphasized in previous works, mostly case reports, small series, or epidemiological studies, but few are known about its real clinical outcomes. Here we present a real-world pilot study aiming to understand the frequency and the clinical impact of HHV-6 coinfection in moderate to critically ill patients hospitalized due to COVID-19. SARS-CoV-2 and HHV-6 were evaluated in nasopharyngeal samples at the hospital admission of suspected COVID-19 patients. From 173 consecutive cases, 60 were SARS-CoV-2 positive and 13/60 (21.7%) were HHV-6 positive after identified as the HHV-6B species by a Sanger sequencing. The SARS-CoV-2+/HHV-6+ group was younger but not significant for cardiovascular diseases, diabetes, obesity, and cancer, but significant among therapeutic immunosuppressed patients (as systemic lupus erythematosus and kidney transplant patients). In the medical records, only sparse data on cutaneous or neurological manifestations were found. Biochemical and hematological data showed only a trend towards hyperferritinemic status and lymphopenia. In conclusion, despite the impressive high frequency of HHV-6 coinfection in SARS-CoV-2 positive cases, it did not impact general mortality. We suggest larger future prospective studies to better elucidate the influence of HHV-6 reactivation in cases of COVID-19, designed to specific assessment of clinical outcomes and viral reactivation mechanisms.

Association of Polymorphisms in the Glutathione S-Transferase Theta-1 Gene with Cirrhosis and Hepatocellular Carcinoma in Brazilian Patients with Chronic Hepatitis C.

Oxidative stress contributes to hepatitis C virus (HCV)-induced liver damage. Host genetic factors may be involved in progression of HCV infection. The present study was conducted to determine the influence of glutathione S-transferase (GST)-M1 and T1 gene polymorphisms during different stages of HCV infection, including chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The study population comprised 190 patients (47 with chronic hepatitis, 83 with cirrhosis (without HCC), and 60 with HCC). GSTM1 and GSTT1 gene polymorphisms were analyzed via multiplex polymerase chain reaction. The GSTT1-null genotype was more commonly detected in patients with cirrhosis (n = 17; 20.5%) and HCC (n = 13; 21.7%) than those with chronic hepatitis (n = 3; 6.4%). The differences in GSTT1-null genotype frequencies were significant for cirrhosis vs. chronic hepatitis (odds ratio, OR, 3.778 (95% confidence interval, CI, 1.045-13.659); p = 0.043) and HCC vs. chronic hepatitis (OR, 4.057 (95% CI, 1.083-15.201); p = 0.038) groups. However, the incidence of individual GSTM1-null or combined GSTM1/GSTT1 double-null genotypes did not vary significantly between the groups. Our collective findings support the utility of the GSTT1-null genotype as a useful biomarker for liver disease progression in Brazilian patients with chronic hepatitis C.

Viral and Prion Infections Associated with Central Nervous System Syndromes in Brazil.

Virus-induced infections of the central nervous system (CNS) are among the most serious problems in public health and can be associated with high rates of morbidity and mortality, mainly in low- and middle-income countries, where these manifestations have been neglected. Typically, herpes simplex virus 1 and 2, varicella-zoster, and enterovirus are responsible for a high number of cases in immunocompetent hosts, whereas other herpesviruses (for example, cytomegalovirus) are the most common in immunocompromised individuals. Arboviruses have also been associated with outbreaks with a high burden of neurological disorders, such as the Zika virus epidemic in Brazil. There is a current lack of understanding in Brazil about the most common viruses involved in CNS infections. In this review, we briefly summarize the most recent studies and findings associated with the CNS, in addition to epidemiological data that provide extensive information on the circulation and diversity of the most common neuro-invasive viruses in Brazil. We also highlight important aspects of the prion-associated diseases. This review provides readers with better knowledge of virus-associated CNS infections. A deeper understanding of these infections will support the improvement of the current surveillance strategies to allow the timely monitoring of the emergence/re-emergence of neurotropic viruses.

Low prevalence of human gammaherpesvirus 8 (HHV-8) infection among HIV-infected pregnant women in Rio De Janeiro, Brazil.

Pregnant women coinfected with the human immunodeficiency virus (HIV) and human gammaherpesvirus 8 (HHV-8) are at higher risk of Kaposi's sarcoma development, increased viral load, and vertical transmission of these viruses. A total of 131 pregnant women infected with HIV were examined for antibodies against HHV-8 latency-associated nuclear antigen (LANA) and lytic antigens using immunofluorescence assays. The presence of HHV-8 DNA was confirmed using real-time polymerase chain reaction (qPCR) and nested PCR. Overall, 0.8% (1/131) of the patients contained antibodies to HHV-8 LANA and lytic antigens, and no HHV-8 DNA was detected. This study, including a small population of HIV-infected pregnant women in Brazil, indicates a low prevalence of HHV-8 seropositivity and absence of active infection in this group. However, a potential role of HHV-8 in the increased transmission and pathogenic activity of HIV in pregnant women is suggested. Attention should be given to the emergence of HHV-8 infection in this population group in order to avoid comorbidities and transmission of HIV.

Seroprevalence of human alphaherpesvirus 1 and 2 among pregnant women infected or uninfected with Zika virus from Rio de Janeiro, Brazil.

Pregnant women are an important group to be monitored for infection due to the risk of transmitting infections to their babies. Both herpes simples virus (HSV) and Zika virus (ZIKV) are neurotropic viruses that can be transmitted congenitally. In this study, the prevalence and risk factors of HSV among Zika-positive and -negative pregnant women from Rio de Janeiro, Brazil, were evaluated and compared. About 167 serum samples included in our study were from pregnant women with ZIKV infection symptoms, who were attended to in different hospitals in Rio de Janeiro between November 2015 to February 2016. Blood samples collected from 167 pregnant women were used for this study. The presence of HSV antibodies and viremia were evaluated by commercial ELISA and quantitative real-time polymerase chain reaction analyses, respectively. The data obtained from medical records were statistically analyzed. The HSV-1 and HSV-2 prevalence among pregnant women was 80.2% and 12.5% for Zika-positive women and 84.5% and 5.6% for Zika-negative women, respectively. None of the pregnant women exhibited HSV viremia. Age, trimester of gestation, and skin color were associated with HSV-1 and HSV-2 prevalence among the groups studied. HSV-2 was more prevalent in Zika-positive pregnant women than in Zika-negative pregnant women, and this simultaneous infection should be better investigated in future studies.

Persistence of Parvovirus B19 in liver from transplanted patients with acute liver failure.

Aim: In this study, we investigated the presence of B19V in liver tissues from patients with acute liver failure (ALF) and evaluated the viral activity in infected liver. Methods: Serum and liver samples from 30 patients who underwent liver transplantation for ALF were investigated for B19V infection by real-time PCR, serological tests and examination of B19V mRNA (transcript) expression in the liver. Results: The serum and liver samples from seven patients were B19V DNA positive (103-105 copies/ml). Most of them presented detectable anti-B19V IgG, indicating persistent infection. B19V mRNA was detected in all patients, demonstrating intra-hepatic replication. Conclusion: B19V infection of the liver during the course of non-A-E ALF suggested a role of B19V, which produced the worst outcome in co-infected patients and in patients with cryptogenic ALF, in liver damage.

Evaluation of HBV-Like Circulation in Wild and Farm Animals from Brazil and Uruguay.

The origin of the hepatitis B virus is a subject of wide deliberation among researchers. As a result, increasing academic interest has focused on the spread of the virus in different animal species. However, the sources of viral infection for many of these animals are unknown since transmission may occur from animal to animal, human to human, animal to human, and human to animal. The aim of this study was to evaluate hepadnavirus circulation in wild and farm animals (including animals raised under wild or free conditions) from different sites in Brazil and Uruguay using serological and molecular tools. A total of 487 domestic wild and farm animals were screened for hepatitis B virus (HBV) serological markers and tested via quantitative and qualitative polymerase chain reaction (PCR) to detect viral DNA. We report evidence of HBsAg (surface antigen of HBV) and total anti-HBc (HBV core antigen) markers as well as low-copy hepadnavirus DNA among domestic and wild animals. According to our results, which were confirmed by partial genome sequencing, as the proximity between humans and animals increases, the potential for pathogen dispersal also increases. A wider knowledge and understanding of reverse zoonoses should be sought for an effective One Health response.

Sexually transmitted infections among HIV-infected and HIV-uninfected women in the Tapajós region, Amazon, Brazil: Self-collected vs. clinician-collected samples.

The anogenital prevalence of sexually transmitted infections (STIs) and the use of cervico-vaginal self-collected vs. clinician-collected samples were evaluated for the diagnosis of human immunodeficiency virus (HIV)-infected and HIV-uninfected women in the Tapajós region, Amazon, Brazil. We recruited 153 women for a cross-sectional study (112 HIV-uninfected and 41 HIV-infected) who sought health services. Anal and cervical scrapings and cervico-vaginal self-collection samples were collected. Real-time polymerase chain reaction methods were used for Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis and Mycoplasma genitalium. A syphilis test was also performed. Risk factors for STIs were identified by multivariate analysis. The overall prevalence of STIs was 30.4% (34/112) in HIV-uninfected women and 24.4% (10/41) in HIV-infected women. Anogenital Chlamydia trachomatis infection was the most prevalent in both groups of women (20.5% vs 19.5%). There was significant agreement for each STI between self-collected and clinician-collected samples: 91.7%, kappa 0.67, 95% confidence interval (CI) 0.49-0.85 for Chlamydia trachomatis; 99.2%, kappa 0.85, 95% CI 0.57-1.00 for Neisseria gonorrhoeae; 97.7%, kappa 0.39, 95% CI -0.16-0.94 for Trichomonas vaginalis; and 94.7%, kappa 0.51, 95% CI 0.20-0.82 for Mycoplasma genitalium. Women with human papillomavirus had coinfection or multiple infections with other STIs. Risk factors for STIs were being ≤ 25 years old, being employed or a student, reporting a history of STI and having a positive HPV test. A high prevalence of STIs in women in the Tapajós region was found. Cervico-vaginal self-collection is a useful tool for STI screening and can be used in prevention control programs in low-resource settings, such as in northern Brazil.

Accuracy of rapid test for diagnosis of hepatitis A with different infection rate settings and with predictive modeling.

AIM: We evaluated the accuracy of a commercial rapid immunochromatographic test (rapid test [RT]) for hepatitis A (HA) diagnosis and epidemiological studies. MATERIALS & METHODS: The accuracy of a RT was evaluated in laboratory and in field conditions. Predictive modeling estimated the test performance in a hypothetical population. RESULTS: The RT showed sensitivities of 66-86%, and specificities of 21-100%, depending on the antibody isotype (IgM or IgG) analyzed and prevalence of infection. CONCLUSION: The RT is a good alternative for diagnostic in HA outbreaks. The predictive model indicates that it should not be used alone for HA diagnosis in low prevalence populations. These data can be used in the future to strengthen decision-making during the implementation of rapid diagnostic methods in health services.

Cervico-vaginal self-collection in HIV-infected and uninfected women from Tapajós region, Amazon, Brazil: High acceptability, hrHPV diversity and risk factors.

OBJECTIVE: We evaluated acceptability of cervico-vaginal self-collection (CVSC) and prevalence of human papillomavirus (HPV) in Human immunodeficiency virus (HIV)-infected and HIV-uninfected women living in the Tapajós region, Amazon, Brazil. METHODS: Cross-sectional study recruited 153 non-indigenous women (HIV-uninfected, n = 112 and HIV-infected, n = 41) who voluntarily sought assistance in health services. Peripheral blood for HIV screening and cervical scraping (CS) for HPV detection were collected. Women who accepted to perform CVSC received instructions and individual collection kits. Risk factors for high-risk HPV genotypes (hrHPV) were identified by uni- and multivariate analyses. RESULTS: The overall acceptability of CVSC was 87%. Only HIV-infected women had cytological abnormalities (12.2%). Prevalence of any HPV and hrHPV infection was 42.9% and 47.9% for HIV-uninfected and 97.6% and 77.5% for HIV-infected women, respectively. There was significant agreement in the detection of HPV (88%, 0.76, 95% confidence interval [CI], 0.65-0.87) and hrHPV (79.7%, 0.56, 95% CI, 0.41-0.71) between self-collected and clinician-collected samples. The most prevalent hrHPV types were HPV16 and HPV18 in HIV-uninfected and HPV16, HPV51 and HPV59 in HIV-infected women. HIV-infected women with hrHPV infection had multiple hrHPV infections (p = 0.005) and lower CD4 count (p = 0.018). Risk factors for hrHPV infection included being HIV-infected and having five or more sexual partners. CONCLUSIONS: CVSC had high acceptability and high prevalence of hrHPV types in women living in the Tapajós region, Amazon, Brazil.

Effects of RNA interference therapy against herpes simplex virus type 1 encephalitis.

BACKGROUND: Herpetic encephalitis (HSE) is caused mainly by herpes simplex virus type 1 (HSV-1) with an annual incidence of 1-4 cases/million inhabitants. Currently, HSE treatment faces difficulties such as the use of antivirals with elevated toxicity, metabolic side effects and HSV-1 resistance. An alternative to antivirals is the use of small interfering RNA (siRNA) as a viral replication inhibitor. In this work, siRNA targeting the UL-39 region was evaluated for HSE treatment in vivo. METHODS: BALB/c mice were inoculated with HSV-1 and treated with siRNA. The treatment was evaluated through kinetics of HSV-1 replication inhibition, number of siRNA doses administered and treatment with siRNA plus acyclovir. All groups were evaluated for signs of HSE, mortality and HSV-1 replication inhibition. RESULTS: The treated group of the kinetic experiment demonstrated a reduction of HSE signs and an HSV-1 replication inhibition of 43.6-99.9% in the brain and 53-98% in trigeminal ganglia (TG). Animals treated with one or two doses of siRNA had a prolonged survival time, reduced clinical signs of HSE and HSV-1 replication inhibition of 67.7% in brains and 85.7% in TG of animals treated with two doses of siRNA. Also, animals treated with siRNA plus acyclovir demonstrated reduced signs of HSE and mortality, as well as HSV-1 replication inhibition in the brain (83.2%) and TG (74.5%). CONCLUSIONS: These findings demonstrated that siRNA was capable of reducing HSE clinical signs, prolonging survival time and inhibiting HSV-1 replication in mice. Thus, siRNA can be a potential alternative to the standard HSE treatment especially to reduce clinical signs and extend survival time in vivo.

New approaches for the standardization and validation of a real-time qPCR assay using TaqMan probes for quantification of yellow fever virus on clinical samples with high quality parameters.

The development and production of viral vaccines, in general, involve several steps that need the monitoring of viral load throughout the entire process. Applying a 2-step quantitative reverse transcription real time PCR assay (RT-qPCR), viral load can be measured and monitored in a few hours. In this context, the development, standardization and validation of a RT-qPCR test to quickly and efficiently quantify yellow fever virus (YFV) in all stages of vaccine production are extremely important. To serve this purpose we used a plasmid construction containing the NS5 region from 17DD YFV to generate the standard curve and to evaluate parameters such as linearity, precision and specificity against other flavivirus. Furthermore, we defined the limits of detection as 25 copies/reaction, and quantification as 100 copies/reaction for the test. To ensure the quality of the method, reference controls were established in order to avoid false negative results. The qRT-PCR technique based on the use of TaqMan probes herein standardized proved to be effective for determining yellow fever viral load both in vivo and in vitro, thus becoming a very important tool to assure the quality control for vaccine production and evaluation of viremia after vaccination or YF disease.

Serological and molecular evidence of hepadnavirus infection in swine.

INTRODUCTION AND OBJECTIVE: Recently, investigations in a swine herd identified evidence of the existence of a novel member of the Hepadnavirus family endemic in swine. The aim of this study was to investigate the serological and molecular markers of Hepadnavirus circulation in Brazilian domestic swine and wild boar herds, and to evaluate the identity with HBV and other Hepadnaviruses reported previously. MATERIALS AND METHODS: For the study, 376 swine were screened for hepatitis B virus serological markers. Analyses were performed in serum samples using commercial enzyme-linked immunosorbent assay (ELISA) kits (DiaSorin®) for anti-HBc, HBsAg and anti-HBs. Reactive and undetermined swine serum samples were selected to perform DNA viral extraction (QIAamp DNA Mini Kit, Qiagen®), partial genome amplification and genome sequencing. RESULTS: From 376 swine samples analysed, 28 (7.45%) were reactive to anti-HBc, 3 (0.80%) to HBsAg and 6 (1.6%) to anti-HBs. Besides, more 17 (4.52%) swine samples analyzed were classified in the grey zone of the EIA test to anti-HBc and 2 (0.53%) to HBsAg. From 49 samples molecularly analyzed after serological trial, 4 samples showed a positive result for the qualitative PCR for Hepadnavirus. Phylogenetic reconstruction using partial genome sequencing (360 bp) of 3 samples showed similarity with HBV with 90.8-96.3% of identity. CONCLUSIONS: Serological and molecular data showed evidence of the circulation of a virus similar to hepatitis B virus in swine.

Hepatitis A virus: host interactions, molecular epidemiology and evolution.

Infection with hepatitis A virus (HAV) is the commonest viral cause of liver disease and presents an important public health problem worldwide. Several unique HAV properties and molecular mechanisms of its interaction with host were recently discovered and should aid in clarifying the pathogenesis of hepatitis A. Genetic characterization of HAV strains have resulted in the identification of different genotypes and subtypes, which exhibit a characteristic worldwide distribution. Shifts in HAV endemicity occurring in different parts of the world, introduction of genetically diverse strains from geographically distant regions, genotype displacement observed in some countries and population expansion detected in the last decades of the 20th century using phylogenetic analysis are important factors contributing to the complex dynamics of HAV infections worldwide. Strong selection pressures, some of which, like usage of deoptimized codons, are unique to HAV, limit genetic variability of the virus. Analysis of subgenomic regions has been proven useful for outbreak investigations. However, sharing short sequences among epidemiologically unrelated strains indicates that specific identification of HAV strains for molecular surveillance can be achieved only using whole-genome sequences. Here, we present up-to-date information on the HAV molecular epidemiology and evolution, and highlight the most relevant features of the HAV-host interactions.

Infection by Brazilian and Dutch swine hepatitis E virus strains induces haematological changes in Macaca fascicularis.

BACKGROUND: Hepatitis E virus (HEV) has been described as an emerging pathogen in Brazil and seems to be widely disseminated among swine herds. An autochthonous human case of acute hepatitis E was recently reported. To obtain a better understanding of the phenotypic profiles of both human and swine HEV strains, a experimental study was conducted using the animal model, Macaca fascicularis. METHODS: Six cynomolgus monkeys (Macaca fascicularis) were inoculated intravenously with swine HEV genotype 3 that was isolated from naturally and experimentally infected pigs in Brazil and the Netherlands. Two other monkeys were inoculated with HEV genotype 3 that was recovered from Brazilian and Argentinean patients with locally acquired acute and fulminant hepatitis E. The haematological, biochemical, and virological parameters of all animals were monitored for 67 days. RESULTS: Subclinical hepatitis was observed in all monkeys after inoculation with HEV genotype 3 that was recovered from the infected swine and human patients. HEV RNA was detected in the serum and/or faeces of 6 out of the 8 cynomolgus monkeys between 5 and 53 days after inoculation. The mild inflammation of liver tissues and elevations of discrete liver enzymes were observed. Seroconversions to anti-HEV IgM and/or IgG were detected in 7 animals. Reactivities to anti-HEV IgA were also detected in the salivary samples of 3 animals. Interestingly, all of the infected monkeys showed severe lymphopenia and a trend toward monocytosis, which coincided with elevations in alanine aminotransferase and antibody titres. CONCLUSIONS: The ability of HEV to cross the species barrier was confirmed for both the swine (Brazilian and Dutch) and human (Argentinean) strains, thus reinforcing the zoonotic risk of hepatitis E in South America. Cynomolgus monkeys that were infected with HEV genotype 3 developed subclinical hepatitis that was associated with haematological changes. Haematological approaches should be considered in future studies of HEV infection.

Mayaro virus infection in amazonia: a multimodel inference approach to risk factor assessment.

BACKGROUND: Arboviral diseases are major global public health threats. Yet, our understanding of infection risk factors is, with a few exceptions, considerably limited. A crucial shortcoming is the widespread use of analytical methods generally not suited for observational data--particularly null hypothesis-testing (NHT) and step-wise regression (SWR). Using Mayaro virus (MAYV) as a case study, here we compare information theory-based multimodel inference (MMI) with conventional analyses for arboviral infection risk factor assessment. METHODOLOGY/PRINCIPAL FINDINGS: A cross-sectional survey of anti-MAYV antibodies revealed 44% prevalence (n = 270 subjects) in a central Amazon rural settlement. NHT suggested that residents of village-like household clusters and those using closed toilet/latrines were at higher risk, while living in non-village-like areas, using bednets, and owning fowl, pigs or dogs were protective. The "minimum adequate" SWR model retained only residence area and bednet use. Using MMI, we identified relevant covariates, quantified their relative importance, and estimated effect-sizes (ß ± SE) on which to base inference. Residence area (ß(Village)  =  2.93 ± 0.41; ß(Upland) = -0.56 ± 0.33, ß(Riverbanks)  =  -2.37 ± 0.55) and bednet use (ß = -0.95 ± 0.28) were the most important factors, followed by crop-plot ownership (ß  =  0.39 ± 0.22) and regular use of a closed toilet/latrine (ß = 0.19 ± 0.13); domestic animals had insignificant protective effects and were relatively unimportant. The SWR model ranked fifth among the 128 models in the final MMI set. CONCLUSIONS/SIGNIFICANCE: Our analyses illustrate how MMI can enhance inference on infection risk factors when compared with NHT or SWR. MMI indicates that forest crop-plot workers are likely exposed to typical MAYV cycles maintained by diurnal, forest dwelling vectors; however, MAYV might also be circulating in nocturnal, domestic-peridomestic cycles in village-like areas. This suggests either a vector shift (synanthropic mosquitoes vectoring MAYV) or a habitat/habits shift (classical MAYV vectors adapting to densely populated landscapes and nocturnal biting); any such ecological/adaptive novelty could increase the likelihood of MAYV emergence in Amazonia.