Seroprevalence of Dengue, Chikungunya and Zika at the epicenter of the congenital microcephaly epidemic in Northeast Brazil: A population-based survey

High Burden of Dengue and Chikungunya Virus in Paraguay: Seroprevalence Findings From Blood Donors

The rise of reemerging pathogens such as DENV and CHIKV presents a major public health threat. With half the global population at risk, Paraguay experiences particularly high infection rates. Despite this, data on the seroprevalence of these viruses in this country is lacking. This study aims to assess the seroprevalence of anti-DENV IgG and anti-CHIKV IgG among blood donors in Paraguay. Serum samples from 546 blood donors across seven regional districts and Asunción were collected from March to May 2023. Participants filled out a questionnaire and underwent eligibility screening. Serum samples were tested for anti-DENV IgG and anti-CHIKV IgG antibodies using immunoassays. Data were analyzed using IBM SPSS version 23.0. The median (IQR) age of donors was 34 (26-44), and 47.1% were female. Anti-DENV IgG prevalence was 87.7%, ranging from 73.7% to 100% by location, with an age-related association. Donors aged 18 to 25 had a 79.2% seroprevalence, while those over 46 had the highest at 91.5% (p = 0.010). Anti-CHIKV IgG prevalence was 37.2%, with men showing a seroprevalence nearly 10% higher than women, but no significant age-related differences were observed. Regional variation in CHIKV seroprevalence was not significant. In conclusion, this study suggests a high seroprevalence of both DENV and CHIKV in Paraguayan blood donors. The high DENV seroprevalence reflects the impact of past outbreaks, while the notable CHIKV prevalence underscores the effects of recent outbreaks. Continuous surveillance, improved diagnostics, and effective vector control measures are essential to mitigate these arboviruses' impact in Paraguay.

The spatiotemporal ecology of Oropouche virus across Latin America: a multidisciplinary, laboratory-based, modelling study

BACKGROUND

Latin America has been experiencing an Oropouche virus (OROV) outbreak of unprecedented magnitude and spread since 2023-24 for unknown reasons. We aimed to identify risk predictors of and areas at risk for OROV transmission.

METHODS

In this multidisciplinary, laboratory-based, modelling study, we retrospectively tested anonymised serum samples collected between 2001 and 2022 for studies on virus epidemiology and medical diagnostics in Bolivia, Brazil, Colombia, Costa Rica, Ecuador, and Peru with nucleoprotein-based commercial ELISAs for OROV-specific IgG and IgM antibodies. Serum samples positive for IgG from different ecological regions and sampling years were tested against Guaroa virus and two OROV glycoprotein reassortants (Iquitos virus and Madre de Dios virus) via plaque reduction neutralisation testing (PRNT) to validate IgG ELISA specificity and support antigenic cartography. Three OROV strains were included in the neutralisation testing, a Cuban OROV isolate from the 2023-24 outbreak, a contemporary Peruvian OROV isolate taken from a patient in 2020, and a historical OROV isolate from Brazil. We analysed the serological data alongside age, sex, cohort, and geographical residence data for the serum samples; reported OROV incidence data; and vector occurrence data to explore OROV transmission in ecologically different regions of Latin America. We used the MaxEnt machine learning methodology to spatially analyse and predict OROV infection risk across Latin America, fitting one model with presence-absence serological data (seropositive results were recorded as presence and seronegative results were recorded as absence) and one model with presence-only, reported incidence data from 2024. We computed marginal dependency plots, variable contribution, and permutation metrics to analyse the impact of socioecological predictors and fitted a generalised linear mixed-effects model with logit link and binary error structure to analyse the potential effects of age, sex, or cohort type bias and interactions between age or sex and cohort type in our serological data. We conducted antigenic cartography and evolutionary characterisations of all available genomic sequences for all three OROV genome segments from the National Center for Biotechnology Information, including branch-specific selection pressure analysis and the construction of OROV phylogenetic trees.

FINDINGS

In total, 9420 serum samples were included in this study, representing 76 provinces in the six Latin American countries previously mentioned. The sex distribution across the combined cohorts was 48% female (4237 of 8910 samples with available data) and 52% male (4673 of 8910 samples) and the mean age was 29·5 years (range 0-95 years). The samples were collected from census-based cohorts, cohorts of healthy individuals, and cohorts of febrile patients receiving routine health care. The average OROV IgG antibody detection rate was 6·3% (95% CI 5·8-6·8), with substantial regional heterogeneity. The presence-absence, serology-based model predicted high-risk areas for OROV transmission in the Amazon River basin, around the coastal and southern areas of Brazil, and in parts of central America and the Caribbean islands, consistent with case data from the 2023-24 outbreak reported by the Pan American Health Organization. Areas with a high predicted risk of OROV transmission with the serology-based model showed a statistically significant positive correlation with state-level incidence rates per 100 000 people in 2024 (generalised linear model, p=0·0003). The area under the curve estimates were 0·79 (95% CI 0·78-0·80) for the serology-based model and 0·66 (95% CI 0·65-0·66) for the presence-only incidence-based model. Longitudinal diagnostic testing of serum samples from cohorts of febrile patients suggested constant circulation of OROV in endemic regions at varying intensity. Climate variables accounted for more than 60% of variable contribution in both the serology-based and incidence-based models. Antigenic cartography, evolutionary analyses, and in-vitro growth comparisons showed clear differentiation between OROV and its glycoprotein reassortants, but not between the three different OROV strains. PRNT titres of OROV-neutralising serum samples were strongly correlated between all three tested OROV isolates (r>0·83; p<0·0001) but were not correlated with the two glycoprotein reassortants.

INTERPRETATION

Our data suggest that climatic factors are major drivers of OROV spread and were potentially exacerbated during 2024 by extreme weather events. OROV glycoprotein reassortants, but not individual OROV strains, probably have distinct antigenicity. Preparedness for OROV outbreaks requires enhanced diagnostics, surveillance, and vector control in current and future endemic areas, which could all be informed by the risk predictions presented in this Article.

FUNDING

European Union.

TRANSLATIONS

For the Spanish and Portuguese translations of the abstract see Supplementary Materials section.

[The efficiency of the rapid chikungunya test in a scenario of Zika and dengue cocirculation in the municipality of Rio de Janeiro, Brazil]

The municipality of Rio de Janeiro is one of the most affected by the simultaneous circulation of the chikungunya (CHIKV), the Zika (ZIKV) and the dengue viruses (DENV) in Brazil. Although rapid tests are commercially available in the country, there are still doubts about their efficacy in flavivirus cocirculation scenarios. This this study aimed to evaluate the performance and best cut-off point of CHIKV rapid tests in a scenario of cocirculation of Zika and dengue in the Rio de Janeiro. A total of 2,120 volunteers who lived in permanent private households in Rio de Janeiro were included and tested for CHIKV using the rapid test Dual Path Platform (DPP). Of the total number of participants, 769 had venous blood samples collected for diagnostic confirmation by the gold standard plaque reduction neutralization test (PRNT) and tested for CHIKV, DENV and ZIKV. The receiver operating characteristic (ROC) curve was used to calculate sensitivity, specificity, positive and negative predictive values, and the best cut-off point. A total of 15.5% of the samples were identified as having previous exposure to CHIKV according to the rapid test and 20.4% of the samples had previous exposure to CHIKV according to the PRNT. We identified prior exposure to DENV in 89.2% of the samples tested using PRNT and 67.8% to ZIKV. The sensitivity and specificity found for the manufacturer's cut-off point was 96.1% and 97.5%, respectively. The best cut-off point found for the rapid test was ≥ 14, a result for which the accuracy was 97.7%, with specificity and sensitivity of 97.9% and 96.8%, respectively. It was concluded that the rapid test has high performance to detect CHIKV infection in a scenario of cocirculation of Zika and dengue.

A prospective, multi-centric study on the prevalence of dengue, zika and chikungunya in asymptomatic blood donors from different geographical regions of Brazil

BACKGROUND AND OBJECTIVES

Arboviruses outbreaks are increasing in their frequency, geographical area and extension. Brazil is one of the most affected countries in the world, due to its tropical weather and favourable mosquito proliferation conditions. During outbreaks, the safety of the blood supply is a concern, in spite of the low number of transfusion-transmitted cases with clinical impact. The aim of this study was to evaluate the use of NAT for Dengue, Zika and Chikungunya RNA in actual screening.

MATERIALS AND METHODS

Blood donors from services located in 4 Brazilian regions were invited to participate in the study and provide an extra blood sample during the collection period between February 7, 2020, and April 4, 2020. Plasma from 21 341 donations was tested in mini pools of 6 by a duplex NAT for Dengue and Chikungunya, in addition to a Zika single assay. Confirmed viremic samples were submitted to an alternative NAT and serological assays.

RESULTS

There were 33 (0.15%) Dengue RNA+ and 5 (0.02%) Chikungunya RNA+ donations. The South region showed the highest prevalence of Dengue-infected donors (0.29%). These results are in line with the incidence of these arboviruses on the respective geographical regions. Viremic units were discarded and blood services notified.

CONCLUSION

Screening blood donors for arboviruses during the outbreak season in Brazil reveals a significant number of viremic individuals. Arbovirus NAT testing is feasible and may be incorporated to the current screening policy.

Seroprevalence of dengue, Zika, and chikungunya in São Sebastião, Brazil (2020-2021): a population-based survey

BACKGROUND

Urban arboviruses pose a significant global burden, particularly in tropical regions like Brazil. São Sebastião, a lower-middle-class urban area just 26 km from the Brazilian capital, is an endemic area for dengue. However, asymptomatic cases may obscure the actual extent of the disease. In this study, we measured the seroprevalence of dengue, Zika virus, and chikungunya, and compared these findings with surveillance data.

METHODS

A cross-sectional study was conducted involving 1,535 households. ELISA serological tests were performed to detect IgM and IgG antibodies against dengue, Zika virus, and chikungunya. History of previous exposure to arboviruses, data on age, gender, and education level were collected through a questionnaire. Participants who tested positive for IgM and/or IgG were classified as soropositive. Statistical analyses included tests for normality, associations, mean comparisons, and correlations. Positive serological results were compared with cases captured by local epidemiological surveillance.

RESULTS

The study included 1,405 individuals, divided into two groups related to pre-pandemic and pandemic COVID-19 phases. Among participants, 0.7% to 28.8% self-reported history of dengue, Zika, or chikungunya. However, the estimated overall seroprevalence was 64.3% (95% CI: 61.8-66.7) for dengue virus, 51.4% (95% CI: 48.8-53.9) for Zika virus, and 5.4% (95% CI: 4.4-6.7) for chikungunya virus. Multiple arboviruses were noted at 4.0% (95% CI: 3.1-5.1). Advancing age and lower education were associated with higher exposure to arboviruses (p < 0.05). The estimated number of urban arboviral infections was 84 times higher than reported cases.

CONCLUSIONS

The large gap between seroprevalence estimates and cases captured by epidemiological surveillance suggests a silent circulation of arboviruses, highlighting the need for comprehensive serological surveys in endemic regions. Addressing these discrepancies is crucial for effective resource allocation and implementation of public health interventions.

Safety and immunogenicity of a live-attenuated chikungunya virus vaccine in endemic areas of Brazil: interim results of a double-blind, randomised, placebo-controlled phase 3 trial in adolescents

BACKGROUND

Chikungunya outbreaks have been reported in Brazil since 2014. Adolescents are a sensitive population who would benefit from a prophylactic vaccine. This study assessed the immunogenicity and safety of the vaccine VLA1553 in adolescents in Brazil. With an overall trial duration of 12 months, we now report data on safety and immunogenicity over a period of 28 days after vaccination.

METHODS

In this double-blind, randomised, placebo-controlled phase 3 trial, adolescents aged 12 to <18 years were recruited. The trial was performed at ten trial sites across Brazil. Eligible participants were generally healthy. The main exclusion criteria comprised immune-mediated or chronic arthritis or arthralgia, a known or suspected defect of the immune system, or any live vaccine received within the 4 weeks before trial vaccination. Randomisation was stratified by baseline serostatus in a 2:1 ratio to receive VLA1553 (at a dose of 1 × 104 TCID50 per 0·5 mL [ie, 50% tissue culture infectious dose]) or placebo. VLA1553 or placebo was administered intramuscularly as a single-dose immunisation on day 1. The primary endpoint was the proportion of baseline seronegative participants with chikungunya virus neutralising antibody levels of 150 or more in μPRNT50 (a micro plaque reduction neutralisation test), which was considered a surrogate of protection. The safety analysis included all participants receiving a trial vaccination. Immunogenicity analyses were performed in a subset. The trial is registered with ClinicalTrials.gov, NCT04650399.

FINDINGS

Between Feb 14, 2022, and March 14, 2023, 754 participants received a trial vaccination (502 received VLA1553 and 252 received placebo) with a per-protocol population of 351 participants for immunogenicity analyses (303 in the VLA1553 group and 48 in the placebo group). In participants who were seronegative at baseline, VLA1553 induced seroprotective chikungunya virus neutralising antibody levels in 247 of 250 (98·8%, 95% CI 96·5-99·8) participants 28 days after vaccination. In seropositive participants, the baseline seroprotection rate of 96·2% increased to 100% after vaccination with VLA1553. Most (365 [93%] of 393) adverse events were of mild or moderate intensity, VLA1553 was generally well tolerated. When compared with placebo, participants exposed to VLA1553 had a significantly higher frequency of related adverse events (351 [69·9%] of 502 vs 121 [48·0%] of 252; p<0·0001), mostly headache, myalgia, fatigue, and fever. Among four reported serious adverse events (three in the VLA1553 group and one in the placebo group), one was classified as possibly related to VLA1553: a high-grade fever. Among 20 adverse events of special interest (ie, symptoms suggesting chikungunya-like disease), 16 were classified as related to trial vaccination (15 in the VLA1553 group and one in the placebo group), with severe symptoms reported in four participants (fever, headache, or arthralgia). 17 adverse events of special interest resolved within 1 week. Among 85 participants with arthralgia (68 in the VLA1553 group and 17 in the placebo group), eight adolescents had short-lived (range 1-5 days), mostly mild recurring episodes (seven in the VLA1553 group and one in the placebo group). The median duration of arthralgia was 1 day (range 1-5 days). The frequency of injection site adverse events for VLA1553 was higher than in the placebo group (161 [32%] vs 62 [25%]), but rarely severe (two [<1%] in the VLA1553 group and one [<1%] in the placebo group). After administration of VLA1553, there was a significantly lower frequency of solicited adverse events in participants who were seropositive at baseline compared with those who were seronegative (53% vs 74%; p<0·0001) including headache, fatigue, fever, and arthralgia.

INTERPRETATION

VLA1553 was generally safe and induced seroprotective titres in almost all vaccinated adolescents with favourable safety data in adolescents who were seropositive at baseline. The data support the use of VLA1553 for the prevention of disease caused by the chikungunya virus among adolescents and in endemic areas.

FUNDING

Coalition for Epidemic Preparedness Innovation and EU Horizon 2020.

TRANSLATION

For the Portuguese translation of the abstract see Supplementary Materials section.

Effect of Sexual Partnerships on Zika Virus Transmission in Virus-Endemic Region, Northeast Brazil

The epidemiologic effects of Zika virus (ZIKV) sexual transmission in virus-endemic countries remain unclear. We conducted a 2-level, linear mixed-effects logistic regression analysis by using a recently acquired population-based ZIKV and chikungunya virus (CHIKV) serologic dataset obtained from persons residing in Northeast Brazil (n = 2,070 participants). We adjusted mathematical models for housing type and age of participants; the models indicated a significantly higher likelihood of ZIKV seropositivity among persons engaged in a sexual relationship within the same household (odds ratio 1.25 [95% CI 1.00-1.55]; p = 0.047), regardless of their partner's ZIKV serostatus, and among participants with a ZIKV-seropositive sex partner within the same household (odds ratio 1.54 [95% CI 1.18-2.01]; p = 0.002). CHIKV was also modeled as a control; no sex-associated effects were observed for CHIKV serology. Inclusion of ZIKV sexual transmission in prevention and control strategies is urgently needed, particularly in ZIKV-endemic regions.

Proceedings of the dengue endgame summit: Imagining a world with dengue control

The first dengue "endgame" summit was held in Syracuse, NY over August 9 and 10, 2023. Organized and hosted by the Institute for Global Health and Translational Sciences at SUNY Upstate Medical University, the gathering brought together researchers, clinicians, drug and vaccine developers, government officials, and other key stakeholders in the dengue field for a highly collaborative and discussion-oriented event. The objective of the gathering was to discuss the current state of dengue around the world, what dengue "control" might look like, and what a potential roadmap might look like to achieve functional dengue control. Over the course of 7 sessions, speakers with a diverse array of expertise highlighted both current and historic challenges associated with dengue control, the state of dengue countermeasure development and deployment, as well as fundamental virologic, immunologic, and medical barriers to achieving dengue control. While sustained eradication of dengue was considered challenging, attendees were optimistic that significant reduction in the burden of dengue can be achieved by integration of vector control with effective application of therapeutics and vaccines.

Clinical spectrum of congenital Zika virus infection in Brazil: Update and issues for research development

This review aimed to provide an update on the morphological and/or functional abnormalities related to congenital Zika virus (ZIKV) infection, based on primary data from studies conducted in Brazil since 2015. During the epidemic years (2015-2016), case series and pediatric cohort studies described several birth defects, including severe and/or disproportionate microcephaly, cranial bone overlap, skull collapse, congenital contractures (arthrogryposis and/or clubfoot), and visual and hearing abnormalities, as part of the spectrum of Congenital Zika Syndrome (CZS). Brain imaging abnormalities, mainly cortical atrophy, ventriculomegaly, and calcifications, serve as structural markers of CZS severity. Most case series and cohorts of microcephaly have reported the co-occurrence of epilepsy, dysphagia, orthopedic deformities, motor function impairment, cerebral palsy, and urological impairment. A previous large meta-analysis conducted in Brazil revealed that a confirmed ZIKV infection during pregnancy was associated with a 4% risk of microcephaly. Additionally, one-third of children showed at least one abnormality, predominantly identified in isolation. Studies examining antenatally ZIKV-exposed children without detectable abnormalities at birth reported conflicting neurodevelopmental results. Therefore, long-term follow-up studies involving pediatric cohorts with appropriate control groups are needed to address this knowledge gap. We recognize the crucial role of a national network of scientists collaborating with international research institutions in understanding the lifelong consequences of congenital ZIKV infection. Additionally, we highlight the need to provide sustainable resources for research and development to reduce the risk of future Zika outbreaks.

Occurrence of hepatitis B and C virus infection in socioeconomic population strata from Recife, Pernambuco, Northeast Brazil

OBJECTIVE

To estimate the probability of infection with hepatitis B (HBV) and C (HCV) viruses in different socioeconomic strata of the population of Recife, Northeast Brazil.

METHODS

Study carried out from samples obtained in a survey of residents of a large urban center that had a population base and stratified sampling with random selection of households using the "Brazil Sample" package in the R software. HBV (HBsAg) and anti-HCV was performed using immunochromatographic tests. In cases positive for HBsAg, anti-HBc and HBeAg were tested using chemiluminescence, as well as HBV-DNA using real-time PCR. For cases positive for anti-HCV, the search for this antibody was repeated by chemiluminescence and for HCV-RNA by real-time PCR. The occurrence of HBsAg and anti-HCV cases in the general population was estimated based on a theoretical negative binomial distribution.

RESULTS

Among 2,070 samples examined, 5 (0.24%) were HBsAg and 2 (0.1%) anti-HCV positive. The majority of cases had self-reported skin color as black/brown (6/7), education level up to high school (6/7), a steady partner (5/7) and lived in an area of low socioeconomic status (5/7).

CONCLUSION

The occurrence of HBsAg and anti-HCV was lower than those previously found in population-based studies and slightly lower than the most recent estimates. Individuals with lower socioeconomic status should be a priority target of public health policies.

A scoping literature review of global dengue age-stratified seroprevalence data: estimating dengue force of infection in endemic countries

BACKGROUND

Dengue poses a significant burden worldwide, and a more comprehensive understanding of the heterogeneity in the intensity of dengue transmission within endemic countries is necessary to evaluate the potential impact of public health interventions.

METHODS

This scoping literature review aimed to update a previous study of dengue transmission intensity by collating global age-stratified dengue seroprevalence data published in the Medline, Embase and Web of Science databases from 2014 to 2023. These data were then utilised to calibrate catalytic models and estimate the force of infection (FOI), which is the yearly per-capita risk of infection for a typical susceptible individual.

FINDINGS

We found a total of 66 new publications containing 219 age-stratified seroprevalence datasets across 30 endemic countries. Together with the previously available average FOI estimates, there are now more than 250 dengue average FOI estimates obtained from seroprevalence studies from across the world.

INTERPRETATION

The results show large heterogeneities in average dengue FOI both across and within countries. These new estimates can be used to inform ongoing modelling efforts to improve our understanding of the drivers of the heterogeneity in dengue transmission globally, which in turn can help inform the optimal implementation of public health interventions.

FUNDING

UK Medical Research Council, Wellcome Trust, Community Jameel, Drugs for Neglected Disease initiative (DNDi) funded by the French Development Agency, Médecins Sans Frontières International; Swiss Agency for Development and Cooperation and UK aid.

Enhanced immunogenicity and protective efficacy in mice following a Zika DNA vaccine designed by modulation of membrane-anchoring regions and its association to adjuvants

Zika virus (ZIKV) is a re-emerging pathogen with high morbidity associated to congenital infection. Despite the scientific advances since the last outbreak in the Americas, there are no approved specific treatment or vaccines. As the development of an effective prophylactic approach remains unaddressed, DNA vaccines surge as a powerful and attractive candidate due to the efficacy of sequence optimization in achieving strong immune response. In this study, we developed four DNA vaccine constructs encoding the ZIKV prM/M (pre-membrane/membrane) and E (envelope) proteins in conjunction with molecular adjuvants. The DNA vaccine candidate (called ZK_ΔSTP), where the entire membrane-anchoring regions were completely removed, was far more immunogenic compared to their counterparts. Furthermore, inclusion of the tPA-SP leader sequence led to high expression and secretion of the target vaccine antigens, therefore contributing to adequate B cell stimulation. The ZK_ΔSTP vaccine induced high cellular and humoral response in C57BL/6 adult mice, which included high neutralizing antibody titers and the generation of germinal center B cells. Administration of ZK-ΔSTP incorporating aluminum hydroxide (Alum) adjuvant led to sustained neutralizing response. In consistency with the high and long-term protective response, ZK_ΔSTP+Alum protected adult mice upon viral challenge. Collectively, the ZK_ΔSTP+Alum vaccine formulation advances the understanding of the requirements for a successful and protective vaccine against flaviviruses and is worthy of further translational studies.

The Antiviral Potential of AdipoRon, an Adiponectin Receptor Agonist, Reveals the Ability of Zika Virus to Deregulate Adiponectin Receptor Expression

Zika virus (ZIKV) is a pathogenic member of the flavivirus family, with several unique characteristics. Unlike any other arbovirus, ZIKV can be transmitted sexually and maternally, and thus produce congenital syndromes (CZS) due to its neurotropism. This challenges the search for safe active molecules that can protect pregnant women and their fetuses. In this context, and in the absence of any existing treatment, it seemed worthwhile to test whether the known cytoprotective properties of adiponectin and its pharmacological analog, AdipoRon, could influence the outcome of ZIKV infection. We showed that both AdipoRon and adiponectin could significantly reduce the in vitro infection of A549 epithelial cells, a well-known cell model for flavivirus infection studies. This effect was particularly observed when a pre-treatment was carried out. Conversely, ZIKV revealed an ability to downregulate adiponectin receptor expression and thereby limit adiponectin signaling.