Long-Term Trends in Mosquito Vector Populations and their Impact on Yellow Fever Outbreaks in Atlantic Forest Fragments of Rio De Janeiro, Brazil (2016-2021)

Among all living beings, mosquitoes account for the highest number of human fatalities. Our study aimed to determine mosquito egg abundance fluctuation from 2015 to 2020, in order to observe which years had the highest mosquito vector densities and whether they coincided with yellow fever virus outbreaks in both human and nonhuman primates. The study area included Atlantic Forest fragments in the state of Rio de Janeiro. Studies from the Diptera Laboratory at FIOCRUZ were selected and compared along a timeline period of the field collections. The highest peak in egg abundance from the analyzed studies was observed from 2016 to 2017 and from 2015 to 2016. The lowest egg abundance was during the collection periods from 2018 to 2019 and 2019 to 2020. The species with the highest abundance throughout all the periods of the studies analyzed was Haemagogus leucocelaenus, representing 87% of all epidemiological species identified. The species with the lowest abundance was Hg. Janthinomys, representing only 1%. Monitoring the population of mosquitoes is imperative for disease surveillance, as the rise in specimens of various vector species directly impacts the occurrence of yellow fever cases in both nonhuman primates and human populations.

Evaluation of humoral immune response after yellow fever infection: an observational study on patients from the 2017-2018 sylvatic outbreak in Brazil

Between 2016 and 2018, Brazil experienced major sylvatic yellow fever (YF) outbreaks that caused hundreds of casualties, with Minas Gerais (MG) being the most affected state. These outbreaks provided a unique opportunity to assess the immune response triggered by the wild-type (WT) yellow fever virus (YFV) in humans. The plaque reduction neutralization test (PRNT) is currently the standard method to assess the humoral immune response to YFV by measuring neutralizing antibodies (nAbs). The present study aimed to evaluate the humoral immune response of patients from the 2017-2018 sylvatic YF outbreak in MG with different disease outcomes by using PRNTs with a WT YFV strain, isolated from the 2017-2018 outbreak, and a vaccine YFV strain. Samples from naturally infected YF patients were tested, in comparison with healthy vaccinees. Results showed that both groups presented different levels of nAb against the WT and vaccine strains, and the levels of neutralization against the strains varied homotypically and heterotypically. Results based on the geometric mean titers (GMTs) suggest that the humoral immune response after a natural infection of YFV can reach higher levels than that induced by vaccination (GMT of patients against WT YFV compared to GMT of vaccinees, P < 0.0001). These findings suggest that the humoral immune responses triggered by the vaccine and WT strains of YFV are different, possibly due to genetic and antigenic differences between these viruses. Therefore, current means of assessing the immune response in naturally infected YF individuals and immunological surveillance methods in areas with intense viral circulation may need to be updated.IMPORTANCEYellow fever is a deadly febrile disease caused by the YFV. Despite the existence of effective vaccines, this disease still represents a public health concern worldwide. Much is known about the immune response against the vaccine strains of the YFV, but recent studies have shown that it differs from that induced by WT strains. The extent of this difference and the mechanisms behind it are still unclear. Thus, studies aimed to better understand the immune response against this virus are relevant and necessary. The present study evaluated levels of neutralizing antibodies of yellow fever patients from recent outbreaks in Brazil, in comparison with healthy vaccinees, using plaque reduction neutralization tests with WT and vaccine YFV strains. Results showed that the humoral immune response in naturally infected patients was higher than that induced by vaccination, thus providing new insights into the immune response triggered against these viruses.

Knowledge and Attitudes Regarding the Vaccination of Brazilian Immigrants in Portugal: Risks When Returning to Their Country of Origin?

Vaccination is one of the main advancements in public health in the prophylaxis of infectious diseases. We intend to describe the general knowledge about vaccines/vaccination among Brazilian immigrants in Portugal, characterize their attitudes toward vaccination, and describe their knowledge of the yellow fever (YF) vaccine. A cross-sectional study was conducted using a self-completion questionnaire (face-to-face or remote). A total of 542 people participated in the study; the mean age was 36.81 years; 40.1% were male; 44.8% had their 12th year of schooling; and 27.0% had resided for ≥10 years in Portugal. Regarding general knowledge about vaccination, 53.8% answered at least 6/8 questions correctly. A total of 37.1% tended to have a favorable attitude toward vaccination. Concerning traveling, 76.7% attributed the risk of disease at the destination as the main reason for accepting vaccines. A total of 89.3% knew that there was a risk of YF in Brazil. A total of 40% answered correctly only one question about the YF vaccine; 21.6% did not answer any questions correctly. Thus, most of the Brazilian immigrants in this study have high general knowledge about vaccines/vaccination, few have a favorable attitude, and their knowledge about the YF vaccine is scarce. This could limit vaccination adherence when visiting Brazil, making health education actions necessary to increase knowledge and prevent YF risks.

Yellow fever - An old foe with new developments

INTRODUCTION

Yellow fever is caused by an RNA flavivirus. Immunisation in conjunction with vector control is at the forefront of yellow fever control and elimination.

OBJECTIVE

This narrative review describes the impact and importance of yellow fever vaccinations for northern Australian health practitioners.

DESIGN

Selected key policies, studies and medical guidelines are reviewed and presented.

FINDING

Large yellow fever outbreaks, associated with vector spread, have occurred in the last decade in Africa and South America, increasing the risk of international spread of the virus. Mobile populations, like travellers or migrant workers, continue to be at risk of yellow fever. Quality assurance, including yellow fever centre accreditation and initiatives to decrease fraudulent yellow fever vaccination documentation, has evolved in the past few years. Fractional dosing of yellow fever vaccines has been shown to provide protection for 1 year in outbreak scenarios, but further studies are needed.

DISCUSSION

Although Australia is yellow fever-free, the disease could be introduced by viraemic persons as a competent Aedes mosquito vector is present in northern Australia. In addition to surveillance and vector control, health education and yellow fever vaccination remain the best lines of defence. In the event of an outbreak, a response via fractional dosing could prove to be effective in controlling the virus.

CONCLUSION

Health care providers in northern Australia should be aware of the risks of yellow fever and its introduction to northern Australia and be able to discuss vaccination status with their clients when needed.

Incidence of anaphylaxis to YF-VAX® yellow fever vaccination: a retrospective evaluation of vaccine adverse event reports 1999-2018

BACKGROUND

The incidence of anaphylaxis after receipt of yellow fever (YF) vaccine is highly variable based upon previously published reports. Anaphylaxis after receiving the YF vaccine has been reported to range from 0 up to 22 per 1 000 000 doses. Our clinical experience suggested increased incidence, which prompted our investigation. We sought to evaluate the current incidence rate of anaphylaxis after receipt of the 17D-204 strain YF-VAX® brand reported in the US.

METHODS

We performed a retrospective review of the Vaccine Adverse Event Reporting System (VAERS) reports of anaphylaxis after receiving the YF-VAX vaccine occurring between 1 October 1999 and 30 September 2018. We utilized the Brighton Collaboration Case Definition and inclusion determination was made by a board-certified allergist. We also obtained the total number of YF-VAX doses distributed across the US during this same time-period and then calculated an updated incidence rate of YF-VAX vaccine-associated anaphylaxis.

RESULTS

We identified 132 potential cases of possible or probable anaphylaxis. Of these, 111 met inclusion criteria: level 1 (n = 51), level 2 (n = 59) and level 3 (n = 1). The manufacturer reported a total distribution of 7 624 160 doses of YF-VAX from 1 October 1999 to 30 September 2018. The calculated incidence rate of YF-VAX vaccine-associated anaphylaxis is estimated at 14.6 events per 1 000 000 doses.

CONCLUSIONS

We conclude the estimated rate of anaphylaxis per VAERS reports is 14.6 events per 1 000 000 doses after YF-VAX vaccination. This is consistent with some previous reports and substantially higher than rates of anaphylaxis after other vaccines.

Mechanisms of Yellow Fever Transmission: Gleaning the Overlooked Records of Importance and Identifying Problems, Puzzles, Serious Issues, Surprises and Research Questions

In viral disease research, few diseases can compete with yellow fever for the volume of literature, historical significance, richness of the topics and the amount of strong interest among both scientists and laypersons. While the major foci of viral disease research shifted to other more pressing new diseases in recent decades, many critically important basic tasks still remain unfinished for yellow fever. Some of the examples include the mechanisms of transmission, the process leading to outbreak occurrence, environmental factors, dispersal, and viral persistence in nature. In this review, these subjects are analyzed in depth, based on information not only in old but in modern literatures, to fill in blanks and to update the current understanding on these topics. As a result, many valuable facts, ideas, and other types of information that complement the present knowledge were discovered. Very serious questions about the validity of the arbovirus concept and some research practices were also identified. The characteristics of YFV and its pattern of transmission that make this virus unique among viruses transmitted by Ae. aegypti were also explored. Another emphasis was identification of research questions. The discovery of a few historical surprises was an unexpected benefit.

YELLOW ALERT: Persistent Yellow Fever Virus Circulation among Non-Human Primates in Urban Areas of Minas Gerais State, Brazil (2021-2023)

Yellow fever virus (YFV) is the agent of yellow fever (YF), which affects both humans and non-human primates (NHP). Neotropical NHP are highly susceptible to YFV and considered sentinels for YFV circulation. Brazil faced a significant YF outbreak in 2017-2018, with over 2000 human cases and 2000 epizootics cases, mainly in the State of Minas Gerais, Brazil. This study aimed to investigate whether YFV circulation persisted in NHP after the human outbreak had subsided. To this end, NHP carcass samples collected in Minas Gerais from 2021 to 2023 were screened for YFV. RNA was extracted from tissue fragments and used in RT-qPCR targeting the YFV 5'UTR. Liver and lung samples from 166 animals were tested, and the detection of the β-actin mRNA was used to ensure adequacy of RNA isolation. YFV RNA was detected in the liver of 18 NHP carcasses collected mainly from urban areas in 2021 and 2022. YFV positive NHP were mostly represented by Callithrix, from 5 out of the 12 grouped municipalities (mesoregions) in Minas Gerais state. These findings reveal the continued YFV circulation in NHP in urban areas of Minas Gerais during 2021 and 2022, with the attendant risk of re-establishing the urban YFV cycle.

Ocular Manifestations of Flavivirus Infections

Flaviviruses are a group of positive-sense, single-stranded RNA viruses predominantly transmitted by arthropods (mainly mosquitoes) that cause severe endemic infections and epidemics on a global scale. They represent a major cause of systemic morbidity and death and are expanding worldwide. Among this group, dengue fever, the West Nile virus, yellow fever, Japanese Encephalitis, and, recently, the Zika virus have been linked to a spectrum of ocular manifestations. These manifestations encompass subconjunctival hemorrhages and conjunctivitis, anterior and posterior uveitis (inclusive of vitritis, chorioretinitis, and retinal vasculitis), maculopathy, retinal hemorrhages, and optic neuritis. Clinical diagnosis of these infectious diseases is primarily based on epidemiological data, history, systemic symptoms and signs, and the pattern of ocular involvement. Diagnosis confirmation relies on laboratory testing, including RT-PCR and serological testing. Ocular involvement typically follows a self-limited course but can result in irreversible visual impairment. Effective treatments of flavivirus infections are currently unavailable. Prevention remains the mainstay for arthropod vector and zoonotic disease control. Effective vaccines are available only for the yellow fever virus, dengue virus, and Japanese Encephalitis virus. This review comprehensively summarizes the current knowledge regarding the ophthalmic manifestations of the foremost flavivirus-associated human diseases.

Enhancing Inactivated Yellow Fever 17D Vaccine-Induced Immune Responses in Balb/C Mice Using Alum/CpG

There are some concerns about the safety of live attenuated yellow fever vaccines (YF-live), particularly viscerotropic adverse events, which have a high mortality rate. The cellular production of the vaccine will not cause these adverse effects and has the potential to extend applicability to those who have allergic reactions, immunosuppression, and age. In this study, inactivated yellow fever (YF) was prepared and adsorbed with Alum/CpG. The cellular and humoral immunities were investigated in a mouse model. The results showed that Alum/CpG (20 μg/mL) could significantly increase the binding and neutralizing activities of the antibodies against YF. Moreover, the antibody level at day 28 after one dose was similar to that of the attenuated vaccine, but significantly higher after two doses. At the same time, Alum/CpG significantly increased the levels of IFN-γ and IL-4 cytokines.

Molecular Characterization of Circulating Yellow Fever Viruses from Outbreak in Ghana, 2021-2022

Yellow fever virus, transmitted by infected Aedes spp. mosquitoes, causes an acute viral hemorrhagic disease. During October 2021-February 2022, a yellow fever outbreak in some communities in Ghana resulted in 70 confirmed cases with 35 deaths (case-fatality rate 50%). The outbreak started in a predominantly unvaccinated nomadic community in the Savannah region, from which 65% of the cases came. The molecular amplification methods we used for diagnosis produced full-length DNA sequences from 3 confirmed cases. Phylogenetic analysis characterized the 3 sequences within West Africa genotype II; strains shared a close homology with sequences from Cote d'Ivoire and Senegal. We deployed more sensitive advanced molecular diagnostic techniques, which enabled earlier detection, helped control spread, and improved case management. We urge increased efforts from health authorities to vaccinate vulnerable groups in difficult-to-access areas and to educate the population about potential risks for yellow fever infections.

Genetic Structuring of One of the Main Vectors of Sylvatic Yellow Fever: Haemagogus (Conopostegus) leucocelaenus (Diptera: Culicidae)

Genetic diversity and population structuring for the species Haemogogus leucocelaenus, a sylvatic vector of yellow fever virus, were found to vary with the degree of agricultural land use and isolation of fragments of Atlantic Forest in municipalities in the state of São Paulo where specimens were collected. Genotyping of 115 mitochondrial SNPs showed that the populations with the highest indices of genetic diversity (polymorphic loci and mean pairwise differences between the sequences) are found in areas with high levels of agricultural land use (northeast of the State). Most populations exhibited statistically significant negative values for the Tajima D and Fu FS neutrality tests, suggesting recent expansion. The results show an association between genetic diversity in this species and the degree of agricultural land use in the sampled sites, as well as signs of population expansion of this species in most areas, particularly those with the highest forest edge densities. A clear association between population structuring and the distance between the sampled fragments (isolation by distance) was observed: samples from a large fragment of Atlantic Forest extending along the coast of the state of São Paulo exhibited greater similarity with each other than with populations in the northwest of the state.

Characterization and Investigation of Risk Factors for Late-Relapsing Hepatitis After Yellow Fever

BACKGROUND

Late-relapsing hepatitis after yellow fever (LHep-YF) during the convalescent phase of the disease has been described during recent yellow fever (YF) outbreaks in Brazil. LHep-YF is marked by a rebound in liver enzymes and nonspecific clinical manifestations around 46-60 days after YF symptom onset.

METHODS

Here we have characterized the clinical course and risk factors for LHep-YF using data from a representative cohort of patients who survived YF in Brazil, 2017-2018. A total of 221 YF-positive patients were discharged from the infectious disease reference hospital in Minas Gerais and were followed up at 30, 45, and 60 days post-symptom onset.

RESULTS

From 46 to 60 days post-symptom onset, 16% of YF patients (n = 36/221) exhibited a rebound of aminotransferases (aspartate aminotransferase or alanine aminotransferase >500 IU/L), alkaline phosphatase, and total bilirubin levels. Other etiologies of liver inflammation such as infectious hepatitis, autoimmune hepatitis, and metabolic liver disease were ruled out. Jaundice, fatigue, headache, and low platelet levels were associated with LHep-YF. Demographic factors, clinical manifestations, laboratory tests, ultrasound findings, and viral load during the acute phase of YF were not associated with the occurrence of LHep-YF.

CONCLUSIONS

These findings provide new data on the clinical course of Late-relapsing hepatitis during the convalescent phase of YF and highlight the need for extended patient follow-up after acute YF.

Accuracy of yellow fever case definition of epidemiologic surveillance, São Paulo, 2018

OBJECTIVE

To evaluate the accuracy of yellow fever (YF) suspected case definitions from the Brazilian Ministry of Health (BMH) and World Health Organization (WHO), as well as propose and evaluate new definitions of suspected cases, considering confirmed and discarded cases.

METHODS

The retrospective study was conducted at the Instituto de Infectologia Emílio Ribas (IIER), using the Epidemiologic Surveillance Form of YF cases. From the confirmed and discarded cases of YF, a logistic regression model was developed. The independent variables were used in a proposed definition of a suspected case of YF and its accuracy was evaluated.

RESULTS

In total, 113 YF suspect cases were reported, with 78 confirmed (69.0%). The definitions by BMH and WHO presented low sensitivity, 59% and 53.8%, and reduced accuracy, 53.1% and 47.8%, respectively. Predictive factors for YF were thrombocytopenia, leukopenia, and elevation of transaminases greater than twice normal. The definition including individual with acute onset of fever, followed by elevation of ALT or AST greater than twice the reference value AND leukopenia OR thrombocytopenia presented high sensitivity (88.3%), specificity (62.9%), and the best accuracy (80.4%), as proposed in the model.

CONCLUSION

The YF suspected case definitions of the BMH and the WHO have low sensitivity. The inclusion of nonspecific laboratory tests increases the accuracy of YF definition.

A Comparison of the Awareness, Attitude, and Uptake of COVID-19, Hepatitis B Virus, and Yellow Fever Vaccines Between Rural and Urban Respondents in Edo State, Nigeria

INTRODUCTION

Despite the target set by WHO, Africa still falls short when it comes to individuals' use of COVID-19 vaccines. There is a similar pattern of low vaccine usage for the hepatitis B virus (HBV) and yellow fever (YF).

AIM AND OBJECTIVE

The objective of our study is to compare the awareness, attitude, and uptake of vaccine-preventable diseases (VPD), COVID-19, HBV, and YF, between a rural and an urban community in Nigeria.

METHODOLOGY

The study was a descriptive cross-sectional study carried out between January 2022 and December 2022 in a rural community, Okada, and an urban community, Benin, in Edo State, Nigeria. A total of 283 rural participants and 483 urban participants were interviewed. SPSS Statistics version 26 (IBM Corp. Released 2019. IBM SPSS Statistics for Windows, Version 26.0. Armonk, NY: IBM Corp.) was used for data collection and analysis. The significant value was set at P<0.05.

RESULTS

A major percentage of both populations, 98.3% urban and 90.1% rural, reported being aware of COVID-19 vaccines (indicated by P<0.001). There was a similar pattern with HBV vaccine awareness. However, awareness of YF vaccines was more common in the rural (63.3%) community than in the urban (55.0%) community. A complete dose uptake of COVID-19 vaccines was reported by 7.7% of the rural and 2.2% of the urban respondents. The major reason for the refusal of vaccine uptake was the fear of possible side effects.

CONCLUSION

The study showed that vaccine uptake for COVID-19, HBV, and YF is low despite seemingly good awareness of these vaccines. The number one reason for any vaccine refusal is the possibility of experiencing side effects.

Safe administration of yellow fever vaccine in patients with suspected egg allergy

Background

The evidence available in the literature on the administration and safety of the yellow fever vaccine in patients with egg allergy is limited.

Objective

We sought to describe the administration of yellow fever vaccine in children with suspected egg allergy using a simplified protocol.

Methods

Children referred to the service from February 2018 to January 2020 with a history of possible egg allergy were classified as probably egg-allergic or not on the basis of history and specific IgE testing. A vaccine prick test was performed only in those with a history of an anaphylactic reaction to egg ingestion and if the result was positive the vaccine was administered in a 2-step protocol (2 equal doses of 0.25 mL with an interval of 30 minutes between the 2 applications). All other children received the vaccine as a single dose.

Results

A total of 435 children were evaluated; 48.27% were probably not allergic, and 51.72% were probably allergic to egg, of which 32.88% were considered anaphylactic. A total of 414 (95.2%) children had no vaccine reactions. Of the 21 (4.8%) children who had some reaction, 10 experienced a local reaction, 9 a mild skin reaction distant from the vaccine site, 1 presented local cutaneous reaction distant to the vaccination site, and 1 patient developed possible anaphylaxis. The vaccine prick test did not predict a vaccine reaction (odds ratio, 1.29; 95% CI, 0.25-6.72; P = .67).

Conclusions

Yellow fever vaccine can be safely administered as a single dose in children with a confirmed or suspected egg allergy.

Compliance with yellow fever and measles vaccines in the revaccination program post-hematopoietic cell transplantation

INTRODUCTION

Measles, mumps, rubella, and even poliomyelitis outbreaks have recently perplexed infectious disease clinicians and epidemiologists globally due to the decline in vaccination coverage rates in children and adults. Measles and yellow fever (YF) have represented an increasing burden on the Brazilian public health system in recent decades. Both diseases are preventable by live-attenuated viral vaccines (LAVV), which have restricted use in hematopoietic cell transplant (HCT) recipients.

METHODS

Autologous and allogeneic HCT recipients returning for regular appointments at the outpatient clinic were invited to participate in the study. Patients transplanted for at least 2 years and with a printed copy of the vaccination record were included.

RESULTS

We assessed the vaccination records of 273 HCT recipients after the second year of HCT (193 allogeneic and 80 autologous) and observed lower compliance with the YF vaccine (58 patients, 21.2%) than with the measles vaccine (138 patients, 50.5%, p ≤ .0001). This is the largest published series of YF vaccination in HCT recipients so far. No severe adverse events occurred. Although expected, chronic graft-versus-host disease (GVHD) did not affect the compliance with measles (p = .08) or YF vaccination (p = .7). Indeed, more allogeneic recipients received measles vaccine in comparison with autologous patients (p < .0001), suggesting that chronic GVHD was not the main reason for not being vaccinated. Children and allogeneic HCT were more likely to receive measles vaccine. Time elapsed from HCT >5 years favored both measles and YF vaccination.

CONCLUSION

A better understanding of the reasons for low compliance with LAVV is necessary to overcome this problem.

Modelling Differential Diagnosis of Febrile Diseases with Fuzzy Cognitive Map

The report of the World Health Organization (WHO) about the poor accessibility of people living in low-to-middle-income countries to medical facilities and personnel has been a concern to both professionals and nonprofessionals in healthcare. This poor accessibility has led to high morbidity and mortality rates in tropical regions, especially when such a disease presents itself with confusable symptoms that are not easily differentiable by inexperienced doctors, such as those found in febrile diseases. This prompted the development of the fuzzy cognitive map (FCM) model to serve as a decision-support tool for medical health workers in the diagnosis of febrile diseases. With 2465 datasets gathered from four states in the febrile diseases-prone regions in Nigeria with the aid of 60 medical doctors, 10 of those doctors helped in weighting and fuzzifying the symptoms, which were used to generate the FCM model. Results obtained from computations to predict diagnosis results for the 2465 patients, and those diagnosed by the physicians on the field, showed an average of 87% accuracy for the 11 febrile diseases used in the study. The number of comorbidities of diseases with varying degrees of severity for most patients in the study also covary strongly with those found by the physicians in the field.

Frequency of allergic reactions in egg allergic patients after receiving the yellow fever vaccine

BACKGROUND

Immunization with live attenuated viral yellow fever vaccine (YFV) grants effective immunity in most cases, and is recommended and prioritized for residents and travelers of endemic countries. YFV is seldom administered to egg-allergic patients (EAP) since it is cultivated in embryonated chicken eggs and may contain residual egg proteins, being a problem for egg-allergic residents and travelers of endemic countries.

OBJECTIVE

Describe the frequency of allergic reactions after YFV administration in confirmed EAP from an allergy outpatient center in Bogotá, Colombia.

METHODS

An observational, retrospective, cross-sectional, and descriptive study was conducted from January 2017 to December 2019. EAP whose allergy was confirmed with a positive Skin Prick Test (SPT) and/or egg protein-specific IgE levels who hadn't received the YFV were included. Every patient had an SPT, severe EAP, and an additional Intradermal Test (IDT) done with the vaccine. If the vaccine SPT and IDT were negative, the YFV was administered as a single dose; if either were positive, the YFV was administered in graded doses. Statistical analysis was done in Stata16MP.

RESULTS

Seventy one patients were included, 24 (33.8%) of those had a history of egg anaphylaxis. All patients had negative YFV SPTs, and two of the five YVF IDTs were positive. Two patients, with previous egg-anaphylaxis, presented allergic reactions to the vaccine.

CONCLUSIONS

YFV did not trigger allergic reactions in EAP without history of egg-anaphylaxis. With further research, safe single-dose vaccination to this population could be considered; however, patients with previous egg-anaphylaxis should be evaluated by an allergist before vaccination.

Yellow fever disease severity and endothelial dysfunction are associated with elevated serum levels of viral NS1 protein and syndecan-1

Yellow fever virus (YFV) infections can cause severe disease manifestations, including hepatic injury, endothelial damage, coagulopathy, hemorrhage, systemic organ failure, and shock, and are associated with high mortality in humans. While nonstructural protein 1 (NS1) of the related dengue virus is implicated in contributing to vascular leak, little is known about the role of YFV NS1 in severe YF and mechanisms of vascular dysfunction in YFV infections. Here, using serum samples from qRT-PCR-confirmed YF patients with severe (n=39) or non-severe (n=18) disease in a well-defined hospital cohort in Brazil, plus samples from healthy uninfected controls (n=11), we investigated factors associated with disease severity. We developed a quantitative YFV NS1 capture ELISA and found significantly increased levels of NS1, as well as syndecan-1, a marker of vascular leak, in serum from severe YF as compared to non-severe YF or control groups. We also showed that hyperpermeability of endothelial cell monolayers treated with serum from severe YF patients was significantly higher compared to non-severe YF and control groups as measured by transendothelial electrical resistance (TEER). Further, we demonstrated that YFV NS1 induces shedding of syndecan-1 from the surface of human endothelial cells. Notably, YFV NS1 serum levels significantly correlated with syndecan-1 serum levels and TEER values. Syndecan-1 levels also significantly correlated with clinical laboratory parameters of disease severity, viral load, hospitalization, and death. In summary, this study points to a role for secreted NS1 in YF disease severity and provides evidence for endothelial dysfunction as a mechanism of YF pathogenesis in humans.

Physical Attributes of Tree Holes in the Atlantic Forest Edges: Evaluating Their Association with the Presence and Abundance of Immature Haemagogus leucocelaenus

Sylvatic yellow fever (SYF) was recently a health issue in Brazil (2016-2019) because transmission was facilitated by a high density of vectors, amplifying hosts, and low vaccine coverage of the human population, especially in urban forests in the Southeast Region of Brazil. Moreover, urban forest edges are more likely to have contact between human and sylvatic vector mosquito populations. Here, we show the association between abiotic and biotic features of tree holes as Haemagogus leucocelaenus rearing sites in Cantareira State Park in Atlantic Forest edges. The analyzed physical features of the tree holes were diameter at breast height, tree hole opening diameter, depth, trunk diameter, tree hole volume, collected volume, height (varying from 0.02 to 4.2 m above ground), and the presence of Culicidae species other than Hg. leucocelaenus. We analyzed 105 positive and 68 negative water samples for larval presence and found no differences between them, suggesting the lack of specific physical characteristics in these categories. Hg. leucocelaenus larval abundance was correlated with the collected volume and opening diameter of tree holes. The tree species that most represented negative breeding sites were Euplassa cantareirae, Guarea macrophylla, Psychotria suterella, and Tibouchina pulchra. Four significant clusters as areas with a high risk of SYV were identified by Get-Ordis spatial analysis. Although Hg. leucocelaenus larvae were found in tree holes with high water levels, their occurrence was regulated by that of other mosquito species. Our findings contribute to clarifying immature vector ecology in tree holes related to human exposure to SYF in urban forest edges.

Vector Competence of Aedes albopictus for Yellow Fever Virus: Risk of Reemergence of Urban Yellow Fever in Brazil

The risk of the emergence and reemergence of zoonoses is high in regions that are under the strong influence of anthropogenic actions, as they contribute to the risk of vector disease transmission. Yellow fever (YF) is among the main pathogenic arboviral diseases in the world, and the Culicidae Aedes albopictus has been proposed as having the potential to transmit the yellow fever virus (YFV). This mosquito inhabits both urban and wild environments, and under experimental conditions, it has been shown to be susceptible to infection by YFV. In this study, the vector competence of the mosquito Ae. albopictus for the YFV was investigated. Female Ae. albopictus were exposed to non-human primates (NHP) of the genus Callithrix infected with YFV via a needle inoculation. Subsequently, on the 14th and 21st days post-infection, the legs, heads, thorax/abdomen and saliva of the arthropods were collected and analyzed by viral isolation and molecular analysis techniques to verify the infection, dissemination and transmission. The presence of YFV was detected in the saliva samples through viral isolation and in the head, thorax/abdomen and legs both by viral isolation and by molecular detection. The susceptibility of Ae. albopictus to YFV confers a potential risk of reemergence of urban YF in Brazil.

Use of live viral vaccines after HCT: Still a lot to learn

Revaccination program after HCT is necessary due to the loss of lifelong immunity acquired by previous vaccination or infections. The program is complex and even in a favourable scenario, it takes more than 2 years to be completed. As the complexity of HCT increases (alternative donors, diversity of monoclonal antibodies), studies evaluating the response to vaccination in this population are welcome, especially those that evaluate live attenuated vaccines given their scarcity. Furthermore, measles, mumps, rubella and even yellow fever, and poliomyelitis outbreaks have perplexed infectious diseases clinicians and epidemiologists globally, most of them due to the decline in vaccination coverage rates in children and adults, because of the growth of antivaccine movements around the world. The study of Lin et al. adds important information about measles, mumps and rubella vaccination after HCT.

Modeling mRNA-based vaccine YFV.E1988 against yellow fever virus E-protein using immuno-informatics and reverse vaccinology approach

To surmount constraints of live-attenuated vaccines we have in silico designed mRNA vaccine using envelope protein as a target antigen. From the alignment of 216 envelope proteins, a consensus sequence was obtained which was used for codon optimization. The secondary structure was predicted using Mfold and RNAfold tool. IEDB server was used to predict T-cell and B-cell epitopes, epitope conservancy, immunogenicity, and population coverage. Antigenicity, allergenicity, and toxicity were predicted using Vaxijen, AllerTOP, and ToxinPred tools, respectively. Interactions between MHC and identified epitopes were confirmed by docking and molecular dynamics simulation. In silico immune simulation was done using the C-ImmSim server. Vaccine peptide 3D structure was predicted and validated based on the Ramachandran plot. Finally, we designed the vaccine construct for simulating restriction cloning using the SnapGene tool. Our optimization of consensus E protein is highly immunogenic, conserved, has immune-dominance characteristics, and suggests high translational efficiency in the host cell. We validated the presence of T and B cell epitopes and interestingly we found one CD4+ and four CD8+ T-cell epitopes that satisfied all the criteria of an effective vaccine candidate. We found high-affinity interactions between epitope and HLA alleles that can stimulate the T-cell response. The immune simulation verified the immune cell response to eliminate the antigen. To ensure effective expression of the vaccine, a circular plasmid has been designed using in silico cloning approach for the in vitro transcription process. Obtained results suggest that the vaccine YFV.E1988 will elicit specific immune responses against YFV and it is a potential model ready for laboratory testing. HighlightsThe envelope (E) protein was found to be highly conserved and it has the potential to protect individuals against YFV infection.YFV.E1988 vaccine has been capable to stimulate both the CD8+ and CD4+ T cell, solving the major limitations of the current live-attenuated vaccines against YFV.Presence of T- and B-cell epitopes across the antigen have been validated using several computational tools.Molecular docking ensured the epitope-allele binding and protein-TLR/MR interaction. The vaccine was found to be immune-stimulatory, safe, and stable.The codons were optimized for efficient translation and increased stability into the human host. The UTR regions and poly (A) tail used for the development of YFV.E1988 showed immune stimulatory potential in several experiments.Communicated by Ramaswamy H. Sarma.

Distinct and dynamic activation profiles of circulating dendritic cells and monocytes in mild COVID-19 and after yellow fever vaccination

Dysregulation of the myeloid cell compartment is a feature of severe disease in hospitalized COVID-19 patients. Here, we investigated the response of circulating dendritic cell (DC) and monocyte subpopulations in SARS-CoV-2 infected outpatients with mild disease and compared it to the response of healthy individuals to yellow fever vaccine virus YF17D as a model of a well-coordinated response to viral infection. In SARS-CoV-2-infected outpatients circulating DCs were persistently reduced for several weeks whereas after YF17D vaccination DC numbers were decreased temporarily and rapidly replenished by increased proliferation until 14 days after vaccination. The majority of COVID-19 outpatients showed high expression of CD86 and PD-L1 in monocytes and DCs early on, resembling the dynamic after YF17D vaccination. In a subgroup of patients, low CD86 and high PD-L1 expression were detected in monocytes and DCs coinciding with symptoms, higher age, and lower lymphocyte counts. This phenotype was similar to that observed in severely ill COVID-19 patients, but less pronounced. Thus, prolonged reduction and dysregulated activation of blood DCs and monocytes were seen in a subgroup of symptomatic non-hospitalized COVID-19 patients while a transient coordinated activation was characteristic for the majority of patients with mild COVID-19 and the response to YF17D vaccination.

Experimental Yellow Fever in the Squirrel Monkey (Saimiri spp.): Hematological, Biochemical, and Immunological Findings

Between 2016 and 2018, Brazil experienced the largest sylvatic epidemic of yellow fever virus (YFV). Despite to the magnitude and rapid spread of the epidemic, little is known about YFV dispersion. The study evaluated whether the squirrel monkey is a good model for yellow fever (YF) studies. Methods: Ten animals were infected with 1 × 10⁶ PFU/mL of YFV, with one negative control. Blood samples were collected daily during the first 7 days and at 10, 20 and 30 days post infection (dpi) for detection of viral load and cytokines by RT-qPCR; measurements of AST, ALT, urea and creatinine were taken; IgM/IgG antibodies were detected by ELISA, and hemagglutination inhibition and neutralization tests were performed. The animals exhibited fever, flushed appearance, vomiting and petechiae, and one animal died. Viremia was detected between 1 and 10 dpi, and IgM/IgG antibodies appeared between 4 and 30 dpi. The levels of AST, ALT and urea increased. The immune responses were characterized by expression of S100 and CD11b cells; endothelial markers (VCAM-1, ICAM-1 and VLA-4), cell death and stress (Lysozyme and iNOS); and pro-inflammatory cytokines (IL-8, TNF-α, and IFN-γ) and anti-inflammatory cytokines (IL-10 and TGF-β). The squirrel monkeys showed changes similar to those described in humans with YF, and are a good experimental model for the study of YF.

Experimental Yellow Fever in Squirrel Monkey: Characterization of Liver In Situ Immune Response

Non-human primates contribute to the spread of yellow fever virus (YFV) and the establishment of transmission cycles in endemic areas, such as Brazil. This study aims to investigate virological, histopathological and immunohistochemical findings in livers of squirrel monkeys (Saimiri spp.) infected with the YFV. Viremia occurred 1-30 days post infection (dpi) and the virus showed a predilection for the middle zone (Z2). The livers were jaundiced with subcapsular and hemorrhagic multifocal petechiae. Apoptosis, lytic and coagulative necrosis, steatosis and cellular edema were also observed. The immune response was characterized by the expression of S100, CD11b, CD57, CD4 and CD20; endothelial markers; stress and cell death; pro and anti-inflammatory cytokines, as well as Treg (IL-35) and IL-17 throughout the experimental period. Lesions during the severe phase of the disease were associated with excessive production of apoptotic pro-inflammatory cytokines, such as IFN-γ and TNF-α, released by inflammatory response cells (CD4+ and CD8+ T lymphocytes) and associated with high expression of molecules of adhesion in the inflammatory foci observed in Z2. Immunostaining of the local endothelium in vascular cells and the bile duct was intense, suggesting a fundamental role in liver damage and in the pathogenesis of the disease.

Yellow Fever Vaccine-Related Neurotropic Disease in Brazil Following Immunization with 17DD

The disease burden of yellow fever virus infection (YFV) is quite high in the tropics where vaccination coverage is low. To date, vaccination is the most effective control strategy to mitigate and eliminate the burden of YF disease. The licensed YF vaccines are safe and effective and serious adverse events are rare. Herein, we report three cases of neurological syndrome, compatible with meningoencephalitis following 17DD vaccination. In all cases, YFV-specific IgM antibodies were detected in the cerebrospinal fluid. Our observations confirm the development of YF vaccine-associated neurotropic disease, a rare serious adverse event, from which all three patients have fully recovered without any long-term sequelae. This report reinforces the need for awareness among health professionals to recognize and effectively manage such events in a timely manner.

Evaluation of superabsorbent polymer (SAP) in oviposition traps used in the integrated control of Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1894) (Diptera:Culicidae)

BACKGROUND

Egg collection traps have been studied to assist in the integrated control of arbovirus vectors. Many enhancements have been made over the years.

METHODS

This study evaluated the use of a hydrated superabsorbent polymer (SAP) in the egg collection of Aedes aegypti and Aedes albopictus in ovitraps. An experiment was conducted in the laboratory to determine the minimum concentration of the product to be used in traps in the field to prevent the development of larvae into adults. In the field, the use of polymers has been evaluated using a traditional model of ovitraps. The positive ovitrap index and mean number of eggs per trap indicator were calculated.

RESULTS

In the laboratory, the larvae did not successfully develop to the adult stage, even at the lowest SAP concentration. In the field, the results showed that ovitraps with SAP proved to be effective for egg collection from both species. It was possible to identify sites with the highest concentration of species and expose the ovitraps for a longer period without larval development.

CONCLUSIONS

There is a need for studies on the adequacy of this technology for control programs. However, the results showed that ovitraps with hydrogel were potentiated to capture eggs, configuring themselves as another tool for vector control.

[Historical events in epidemiology, at the Muñiz Hospital, Buenos Aires, Argentina]

The Muñiz hospital is an institution with historical, cultural and health heritage. A historical analysis of the different epidemics/pandemics and outbreaks is carried out here, assessing the epidemiological management (surveillance, prevention, control and emergency management) in the institution and the reason for its architecture. To this end, a systematic review of the literature on the history of the Muñiz hospital and its references was carried out, since 1980 to 2023, following the PRISMA format. Thirty-six publications were found that met the required methodological and epidemiological criteria. The review shows the relevant health problems, the events present in an epidemic/ pandemic, the importance of preventive measures and to assess the need for a continuous epidemiological surveillance system, as well as the contribution of historical methodological references that allow obtaining useful information in the health area. We have addressed great historical moments in epidemiology, explaining the management of diseases or epidemics/pandemics at the Muñiz hospital, which were largely related to the society of the time (paradigms). It should be noted that population growth spread diseases throughout the planet, generating threats, and that epidemics/pandemics transformed societies and quite possibly have decisively changed the course of history, as happened with the COVID-19 pandemic.

Seroconversion and antibody persistence after yellow fever vaccination in people living with HIV: impact of baseline HIV viral load and yellow fever seropositivity

BACKGROUND

Data on seroconversion rates following yellow fever (YF) vaccine and effect of revaccination in people living with HIV (PLWH) are scarce. We aimed at determining key factors for seroconversion after YF vaccine in PLWH and the role of preexisting neutralizing antibodies (NAbs) at vaccination.

METHODS

A retrospective cross-sectional study at several timepoints in two Belgian AIDS Reference Center. For each individual, plasma samples from three timepoints were selected: Timepoint 0 (TP0) in the year before administration of the YF vaccine, Timepoint 1 (TP1) in the year following the YF vaccine, Timepoint 2 (TP2) >1 year after the YF vaccine. Plasma samples were analysed for YF NAbs by plaque reduction neutralization test. The primary endpoint was the number of patients with protective levels of NAbs ≥ 1/10. A boosted immune response was defined as a 4-fold increase in serologic titres following revaccination.

RESULTS

Of the 160 PLWH included, protective levels of NAbs were present in 36%, 87% and 72% of subjects at baseline, at a median of 12 months and a median of 96 months after YF vaccination, respectively. Among vaccine recipients negative for YF NAbs at baseline (n = 102), 83% seroconverted. PLWH with undetectable HIV viral load (VL) at baseline were more likely to seroconvert (P < 0·01). A booster response was observed in only 17% of subjects with baseline seropositivity (n = 10 out of 58). In multivariate analysis, undetectable HIV VL at vaccination and baseline YF seropositivity were associated with persistent levels of protective NAbs at a median of 8 years after YF vaccination.

CONCLUSION

Undetectable HIV VL at baseline is associated with high rates of seroconversion. YF seropositivity before revaccination is associated with low rates of booster effect but a higher chance of long term persistent NAbs response, suggesting a benefit of revaccination in PLWH.

Towards the Laboratory Maintenance of Haemagogus janthinomys (Dyar, 1921), the Major Neotropical Vector of Sylvatic Yellow Fever

Haemagogus (Haemagogus) janthinomys (Dyar, 1921), the major neotropical vector of sylvatic yellow fever virus, is notoriously difficult to maintain in captivity. It has never been reared beyond an F1 generation, and almost no experimental transmission studies have been performed with this species since the 1940s. Herein we describe installment hatching, artificial blood feeding, and forced-mating techniques that enabled us to produce small numbers of F3 generation Hg. janthinomys eggs for the first time. A total of 62.8% (1562/2486) F1 generation eggs hatched during ≤10 four-day cycles of immersion in a bamboo leaf infusion followed by partial drying. Hatching decreased to 20.1% (190/944) in the F2 generation for eggs laid by mosquitoes copulated by forced mating. More than 85% (79/92) female F2 mosquitoes fed on an artificial blood feeding system. While we were unable to maintain a laboratory colony of Hg. janthinomys past the F3 generation, our methods provide a foundation for experimental transmission studies with this species in a laboratory setting, a critical capacity in a region with hyper-endemic transmission of dengue, Zika, and chikungunya viruses, all posing a risk of spillback into a sylvatic cycle.

Back to Where It Was First Described: Vectors of Sylvatic Yellow Fever Transmission in the 2017 Outbreak in Espírito Santo, Brazil

Evidence of sylvatic yellow fever was first reported in Atlantic Forest areas in Espírito Santo, Brazil, during a yellow fever virus (YFV) outbreak in 1931. An entomological survey was conducted in six forest sites during and after an outbreak reported ~80 years after the last case in the area. Among 10,658 mosquitoes of 78 species, Haemagogus leucocelaenus, and Hg. janthinomys/capricornii were considered the main vectors as they had a relatively high abundance, co-occurred in essentially all areas, and showed high YFV infection rates. Sabethes chloropterus, Sa. soperi, Sa. identicus, Aedes aureolineatus, and Shannoniana fluviatilis may have a secondary role in transmission. This is the first report of Sa. identicus, Ae. aureolineatus, and Sh. fluviatilis infected with YFV. Our study emphasizes the importance of entomological monitoring and maintenance of high vaccination coverage in receptive areas to YFV transmission.

Leveraging Lessons Learned from Yellow Fever and Polio Immunization Campaigns during COVID-19 Pandemic, Ghana, 2021

Ghana is a yellow fever-endemic country and experienced a vaccine-derived polio outbreak in July 2019. A reactive polio vaccination campaign was conducted in September 2019 and preventive yellow fever campaign in November 2020. On March 12, 2020, Ghana confirmed its first COVID-19 cases. During February-August 2021, Ghana received 1,515,450 COVID-19 vaccines through the COVID-19 Vaccines Global Access initiative and other donor agencies. We describe how systems and infrastructure used for polio and yellow fever vaccine deployment and the lessons learned in those campaigns were used to deploy COVID-19 vaccines. During March-August 2021, a total of 1,424,008 vaccine doses were administered in Ghana. By using existing vaccination and health systems, officials in Ghana were able to deploy COVID-19 vaccines within a few months with <5% vaccine wastage and minimal additional resources despite the short shelf-life of vaccines received. These strategies were essential in saving lives in a resource-limited country.

Mosquito Fauna and Spatial Distribution in an Atlantic Forest Area in Rio de Janeiro State, Brazil, Reveal a High Risk of Transmission of Yellow Fever and Other Arboviruses

In 2017-2019, Brazil recorded its most severe outbreak of yellow fever due to the spread of the virus (YFV) in the country's southeast. Here, we investigated mosquito fauna and the spatial distribution of species in a primatology center in the Atlantic Forest bioregion in Rio de Janeiro state to evaluate the risk of YFV transmission in distinct environments. Fortnightly mosquito collections were performed from December 2018 to December 2019 at 12 sites along a disturbance gradient from a modified environment to 400 m inside the forest. We used ovitraps, BG-Sentinel, and protected human attraction (PHA). A total of 9349 mosquitoes of 21 species were collected. The collection method strongly influenced the captured fauna, with species such as Anopheles cruzii, Psorophora ferox, Runchomyia cerqueirai, Wyeomyia incaudata, Wy. theobaldi, Sabethes chloropterus, and Sa. albiprivus only collected via PHA. Collections with ovitraps resulted in low diversity and richness, with Haemagogus leucocelaenus and Hg. janthinomys/capricornii predominating. The diverse local fauna and the abundance and ubiquity of the latter species, which are the primary vectors of YFV, indicated that this area was highly vulnerable to arbovirus transmission, especially yellow fever, highlighting the need for improved surveillance and vaccination coverage in human and captive endangered non-human primates.

The COVID-19 Impact on the Trends in Yellow Fever and Lassa Fever Infections in Nigeria

Lassa fever (LF) and yellow fever (YF) belong to a group of viral hemorrhagic fevers (VHFs). These viruses have common features and damages the organs and blood vessels; they also impair the body's homeostasis. Some VHFs cause mild disease, while some cause severe disease and death such as in the case of Ebola or Marburg. LF virus and YF virus are two of the most recent emerging viruses in Africa, resulting in severe hemorrhagic fever in humans. Lassa fever virus is continuously on the rise both in Nigeria and neighboring countries in West Africa, with an estimate of over 500,000 cases of LF, and 5000 deaths, annually. YF virus is endemic in temperate climate regions of Africa, Central America (Guatemala, Honduras, Nicaragua, El Salvador), and South America (such as Brazil, Argentina, Peru, and Chile) with an annual estimated cases of 200,000 and 30,000 deaths globally. This review examines the impact of the COVID-19 pandemic on the trend in epidemiology of these two VHFs to delineate responses that are associated with protective or pathogenic outcomes.

Occurrence of the Sylvatic Yellow Fever Vector Mosquito Haemagogus leucocelaenus (Diptera: Culicidae) in an Atlantic Forest Fragment of the Touristic State of Rio de Janeiro, Brazil

The yellow fever virus is estimated to cause 30,000 deaths each year worldwide, with the majority of cases and deaths occurring in Africa. The virus is also endemic to Central and South America, including northern and western Brazil. The sylvatic cycle of the virus is related to wild and rural areas, with nonhuman primates as the primary host and wild mosquitoes, specifically from the genera Haemagogus, as vectors. The diversity of the mosquito community plays a significant role in the increase of pathogen transmission to humans. In the present study, we detected fluctuation in populations of vector mosquitoes using ovitraps for Culicidae egg collection. The study area is a forest fragment of the Atlantic Forest, one of the most threatened biomes in Brazil. This biome has been suffering significant deforestation due to anthropic activity. Worryingly, the proximity of human populations to forest environments increases the risk of spreading disease from forest fragments to urban areas. Our findings showed that the highest egg abundance occurred in December 2019, with a significant difference (p = 0.005) between rainy and dry seasons. Most eggs were collected during the rainy period. Subsequent quantification of specimens from epidemiologically relevant species hatched from field-collected eggs resulted in 1,131 (86%) Haemagogus leucocelaenus (Dyar & Shannon, 1924), 111 (8%) Aedes terrens (Walker, 1856), 47 (4%) Aedes albopictus (Skuse, 1894), and 21 (2%) Haemagogus janthinomys (Dyar, 1921). Finally, we assessed the behavior of different vector species performing oviposition on the same breeding site. The highest correlation coefficient was observed between Ae. albopictus and Ae. terrens (rho = 0.52) concerning other Culicidae species. Therefore, we believe that Culicidae population surveillance is crucial for disease monitoring since the increase in specimens of a number of vector species influences the emergence of yellow fever cases in nonhuman primates and human populations.

Exotic viral hepatitis: A review on epidemiology, pathogenesis, and treatment

Certain "exotic" viruses are known to cause clinical diseases with potential liver involvement. These include viruses, beyond regular hepatotropic viruses (hepatitis A, -B(D), -C, -E, cytomegalovirus, Epstein-Barr virus), that can be found in (sub)tropical areas and can cause "exotic viral hepatitis". Transmission routes typically involve arthropods (Crimean Congo haemorrhagic fever, dengue, Rift Valley fever, yellow fever). However, some of these viruses are transmitted by the aerosolised excreta of rodents (Hantavirus, Lassa fever), or via direct contact or contact with bodily fluids (Ebola). Although some exotic viruses are associated with high fatality rates, such as Ebola for example, the clinical presentation of most exotic viruses can range from mild flu-like symptoms, in most cases, right through to being potentially fatal. A smaller percentage of people develop severe disease with haemorrhagic fever, possibly with (fulminant) hepatitis. Liver involvement is often caused by direct tropism for hepatocytes and Kupffer cells, resulting in virus-mediated and/or immune-mediated necrosis. In all exotic hepatitis viruses, PCR is the most sensitive diagnostic method. The determination of IgM/IgG antibodies is a reasonable alternative, but cross-reactivity can be a problem in the case of flaviviruses. Licenced vaccines are available for yellow fever and Ebola, and they are currently under development for dengue. Therapy for exotic viral hepatitis is predominantly supportive. To ensure that preventive measures can be introduced to control possible outbreaks, the timely detection of these viruses is very important.

New Insights into the Mechanism of Immune-Mediated Tissue Injury in Yellow Fever: The Role of Immunopathological and Endothelial Alterations in the Human Lung Parenchyma

Yellow fever (YF) may cause lesions in different organs. There are no studies regarding the in situ immune response in the human lung and investigating immunopathological aspects in fatal cases can help to better understand the evolution of the infection. Lung tissue samples were collected from 10 fatal cases of human yellow fever and three flavivirus-negative controls who died of other causes and whose lung parenchymal architecture was preserved. In YFV-positive fatal cases, the main histopathological changes included the massive presence of diffuse alveolar inflammatory infiltrate, in addition to congestion and severe hemorrhage. The immunohistochemical analysis of tissues in the lung parenchyma showed significantly higher expression of E-selectin, P-selectin, ICAM-1, VCAM-1 in addition to cytokines such as IL-4, IL-10, IL-13, TNF- α, IFN-γ and TGF-β compared to the negative control. The increase in immunoglobulins ICAM-1 and VCAM-1 results in strengthening of tissue transmigration signaling. E-selectin and P-selectin actively participate in this process of cell migration and formation of the inflammatory infiltrate. IFN-γ and TNF-α participate in the process of cell injury and viral clearance. The cytokines IL-4 and TGF-β, acting in synergism, participate in the process of tissue regeneration and breakdown. The anti-inflammatory cytokines IL-4, IL-10 and IL-13 also act in the reduction of inflammation and tissue repair. Our study indicates that the activation of the endothelium aggravates the inflammatory response by inducing the expression of adhesion molecules and cytokines that contribute to the rolling, recruitment, migration and eliciting of the inflammatory process in the lung parenchyma, contributing to the fatal outcome of the disease.

Development of a Bicistronic Yellow Fever Live Attenuated Vaccine with Reduced Neurovirulence and Viscerotropism

The yellow fever (YF) live attenuated vaccine strain 17D (termed 17D) has been widely used for the prevention and control of YF disease. However, 17D retains significant neurovirulence and viscerotropism in mice, which is probably linked to the increased occurrences of serious adverse events following 17D vaccination. Thus, the development of an updated version of the YF vaccine with an improved safety profile is of high priority. Here, we generated a viable bicistronic YF virus (YFV) by incorporating the internal ribosome entry site (IRES) from Encephalomyocarditis virus into an infectious clone of YFV 17D. The resulting recombinant virus, 17D-IRES, exhibited similar replication efficiency to its parental virus (17D) in mammalian cell lines, while it was highly restricted in mosquito cells. Serial passage of 17D-IRES in BHK-21 cells showed good genetic stability. More importantly, in comparison with the parental 17D, 17D-IRES displayed significantly decreased mouse neurovirulence and viscerotropism in type I interferon (IFN)-signaling-deficient and immunocompetent mouse models. Interestingly, 17D-IRES showed enhanced sensitivity to type I IFN compared with 17D. Moreover, immunization with 17D-IRES provided solid protection for mice against a lethal challenge with YFV. These preclinical data support further development of 17D-IRES as an updated version for the approved YF vaccine. This IRES-based attenuation strategy could be also applied to the design of live attenuated vaccines against other mosquito-borne flaviviruses. IMPORTANCE Yellow fever (YF) continually spreads and causes epidemics around the world, posing a great threat to human health. The YF live attenuated vaccine 17D is considered the most efficient vaccine available and helps to successfully control disease epidemics. However, side effects may occur after vaccination, such as viscerotropic disease (YEL-AVD) and neurotropic adverse disease (YEL-AND). Thus, there is an urgent need for a safer YF vaccine. Here, an IRES strategy was employed, and a bicistronic YFV was successfully developed (named 17D-IRES). 17D-IRES showed effective replication and genetic stability in vitro and high attenuation in vivo. Importantly, 17D-IRES induced humoral and cellular immune responses and conferred full protection against lethal YFV challenge. Our study provides data suggesting that 17D-IRES, with its prominent advantages, could be a vaccine candidate against YF. Moreover, this IRES-based bicistronic technology platform represents a promising strategy for developing other live attenuated vaccines against emerging viruses.

Wild-type Yellow fever virus in cerebrospinal fluid from fatal cases in Brazil, 2018

Yellow fever virus (YFV) is the causative agent of yellow fever (YF), a hemorrhagic and viscerotropic acute disease. Severe YF has been described in approximately 15-25% of YF patients, with 20-50% of severe YF cases being fatal. Here we analyzed cerebrospinal fluid (CSF) samples collected during the YF outbreak in Brazil in 2018, aiming to investigate CNS neuroinvasion in fatal YFV cases. YFV RNA was screened by RT-qPCR targeting the 3'UTR region of the YFV genome in CSF. CSF samples were tested for the presence of anti-YFV IgM and neutralizing antibodies, coupled with routine laboratory examinations. Among the 13 patients studied, we detected anti-YFV IgM in CSF from eight patients and YFV RNA in CSF from five patients. YFV RNA genomic load in CSF samples ranged from 1.75×103 to 5.42×103 RNA copies/mL. We genotyped YFV from three CSF samples that grouped with other YFV samples from the 2018 outbreak in Brazil within the South-American I genotype. Even though descriptions of neurologic manifestations due to wild type YFV (WT-YFV) infection are rare, since the last YF outbreak in Brazil in 2017-2018, a few studies have demonstrated WT-YFV RNA in CSF samples from YF fatal cases. Serological tests indicated the presence of IgM and neutralizing antibodies against YFV in CSF samples from two patients. Although the presence of viral RNA, IgM and neutralizing antibodies in CSF samples could indicate neuroinvasiveness, further studies are needed to better elucidate the role of YFV neuroinvasion and possible impacts in disease pathogenesis.

Yellow Fever Molecular Diagnosis Using Urine Specimens during Acute and Convalescent Phases of the Disease

Prior studies have demonstrated prolonged presence of yellow fever virus (YFV) RNA in saliva and urine as an alternative to serum. To investigate the presence of YFV RNA in urine, we used RT-PCR for YFV screening in 60 urine samples collected from a large cohort of naturally infected yellow fever (YF) patients during acute and convalescent phases of YF infection from recent YF outbreaks in Brazil (2017 to 2018). Fifteen urine samples from acute phase infection (up to 15 days post-symptom onset) and four urine samples from convalescent phase infection (up to 69 days post-symptom onset), were YFV PCR-positive. We genotyped YFV detected in seven urine samples (five collected during the acute phase and two collected during the YF convalescent phase). Genotyping indicated the presence of YFV South American I genotype in these samples. To our knowledge, this is the first report of wild-type YFV RNA detection in the urine this far out from symptom onset (up to 69 DPS), including YFV RNA detection during the convalescent phase of YF infection. The detection of YFV RNA in urine is an indicative of YFV infection; however, the results of RT-PCR using urine as sample should be interpreted with care, since a negative result does not exclude the possibility of YFV infection. With a possible prolonged period of detection beyond the viremic phase, the use of urine samples coupled with serological tests, epidemiologic inquiry, and clinical assessment could provide a longer diagnostic window for laboratory YF diagnosis.

The Efficacy of the Combination of Naproxen and Fexofenadine (SJP-003) to Prevent or Reduce Side Effects of Receiving Multiple Travel Vaccines: A Case Report

A considerable number of travelers receive multiple travel vaccinations before going on holiday. Here, we present a case report of a 56-year-old male traveler. On day 1, he received vaccinations against influenza, Tdab (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis), MMR (measles, mumps, and rubella), yellow fever, and cholera. On days 1,3, 5, and 7, he self-administered an oral vaccine against typhoid. Treatment comprised the combination of 220 mg naproxen and 180 mg fexofenadine (SJP-003), to be taken 4h before and 6h after the vaccinations on day 1, and every 12 h thereafter until the end of day 7. Side effects were noted daily, and their severity was scored on a scale ranging from 0 (absent) to 10 (severe). These reports revealed that, except from a slight bruising at the injection site, no side effects were experienced from day 1 to day 4. After the second dose on day 3, treatment was discontinued. Two hours after taking the typhoid vaccine on Day 5, various flu-like symptoms were reported of moderate to high severity, including fever, muscle aches (both with severity score of 8), headache (severity score 7), and nausea (severity score 6). Therefore, at 2 h after typhoid vaccination on day 5, naproxen and fexofenadine were self-administered. At 4 h thereafter, all symptoms were resolved. Treatment was continued at the 12 h schedule. On day 6 and 7, no side effects were reported. Taken together, this case study suggests that the combination of naproxen and fexofenadine was effective in preventing or reducing vaccination side effects. Therefore, more research is warranted to further evaluate the efficacy of SJP-003.

Ecology of Aedes vittatus (Diptera: Culicidae) in rock pools across agroecosystem in Northern Savanna, Nigeria

BACKGROUND & OBJECTIVES

This study focuses on modulating dexterity of some ecological variables of Aedes vittatus classically breeding in rocky habitats. The study provides a useful insight into ecological variables that underpin or hinder profuse breeding of Ae. vittatus in rock pools and its probable role in disease transmission.

METHODS

HANNA HI98129 pH/EC/TDS/TEMP meter was used in situ while standard protocols were used to determine other hydro-chemical variables. Aedes vittatus larvae were obtained with soup ladle and modified ladle dippers. D-frame net was used to capture macroinvertebrates while plankton net was used to obtain samples of microalgae. Tadpoles and water turtles were collected with fine mesh invertebrate net. Macrophytes were uprooted and identified at the Herbarium Unit, Department of Botany, Ahmadu Bello University, Zaria. The influence of physicochemical variables was correlated with distribution of Ae. vittatus using Principal Component Analysis. Regression and ANOVA were used to test for association between predictor variables and mosquito abundance and for the difference amongst inselbergs.

RESULTS

Linear larval density of Ae. vittatus in rock pools which tapered across Guinea savanna were obtained from twenty-one sites with average density of 139.6 in Sudan savanna. Guinea savanna had an average larval density of 75.5 with lower subsets of moving average densities compared to Sudan savanna. One hundred and sixty-one aquatic insects belonging to four insect orders cohabited rock pools with Ae. vittatus. Toads and frogs' tadpoles were of Bufonidae and Pyxicephalidae families while water turtles belong to Emydidae. pH, TDS (ppm), EC (μs/cm) and alkalinity (mg/l) differed significantly (p<0.05) with the abundance of Ae. vittatus in rock pools. Temperature, depth, water hardness and total suspended solid had direct influence on the distribution of Ae. vittatus in rock pools across sites. Significant positive correlation exists between aquatic insects and abundance of Ae. vittatus. Hydroperiod length, concentration of nitrate and pH were determinants that leverage profuse breeding of Ae. vittatus and survival of rock pool biota.

INTERPRETATION & CONCLUSION

Results revealed that the bearing influence of rock pool variables is inevitable for breeding of Ae. vittatus. A well defined measure of efficacy incorporating indigenous communities for sustained vector control on inselbergs will go a long way in decimating population of Ae. vittatus and limit the risk of spread of yellow fever hitherto areas not thriving.

Interaction of Haemagogus leucocelaenus (Diptera: Culicidae) and Other Mosquito Vectors in a Forested Area, Rio de Janeiro, Brazil

The yellow fever (YF) virus has been detected throughout Brazil, with the occurrence of human cases, cyclic epizootics, and its isolation from Haemagogus janthinomys and Hg. leucocelaenus. We assessed the seasonal occurrence, egg abundancy, and oviposition interaction of mosquito vector species captured at a Private Natural Heritage Reserve in the Atlantic Forest biome. A total of 2943 eggs and 1538 mosquito larvae were collected from which 1231 belonged to entomologically important species. Ovitraps were used to collect immature mosquitoes from September 2019 to January 2021. The Mann–Whitney test was used to assess the differences in the abundance of eggs between rainy and dry seasons. Kruskal–Wallis and Dunn’s post hoc tests were used to evaluate the significance of the differences in the number of individuals from vector species. The highest percentage of mosquito vector eggs were collected during the rainy season, from December to February. Most eggs recovered from ovitraps belonged to the species Hg. leucocelaenus, representing 85% of all mosquito eggs identified. The other species had lower abundances and percentages: Aedes terrens (7%), Haemagogus janthinomys (5%) and Aedes albopictus (3%). The species that shared breeding sites with a higher frequency were Hg. leucocelaenus and Hg. janthinomys, with a statistically positive correlation (ρ = 0.74). This finding suggests that maybe the presence of Hg. leucocelaenus eggs acted as an attractant for Hg. janthinomys or vice versa. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control approaches directed against specific pathogen vectors of medical and veterinary importance.

Environmental determinants predicting population vulnerability to high yellow fever incidence

Yellow fever (YF) is an endemic mosquito-borne disease in Brazil, though many locations have not observed cases in recent decades. Some locations with low disease burden may resemble locations with higher disease burden through environmental and ecohydrological characteristics, which are known to impact YF burden, motivating increased or continued prevention measures such as vaccination, mosquito control or surveillance. This study aimed to use environmental characteristics to estimate vulnerability to observing high YF burden among all Brazilian municipalities. Vulnerability was defined in three categories based on yearly incidence between 2000 and 2017: minimal, low and high vulnerability. A cumulative logit model was fit to these categories using environmental and ecohydrological predictors, selecting those that provided the most accurate model fit. Per cent of days with precipitation, mean temperature, biome, population density, elevation, vegetation and nearby disease occurrence were included in best-fitting models. Model results were applied to estimate vulnerability nationwide. Municipalities with highest probability of observing high vulnerability was found in the North and Central-West (2000-2016) as well as the Southeast (2017) regions. Results of this study serve to identify specific locations to prioritize new or ongoing surveillance and prevention of YF based on underlying ecohydrological conditions.

Preclinical and clinical experience with dupilumab on the correlates of live attenuated vaccines

Background

The safety and tolerability of live attenuated vaccines in patients administered dupilumab for moderate-to-severe asthma have not been previously evaluated. During the LIBERTY ASTHMA TRAVERSE open-label extension study (ClinicalTrials.gov identifier NCT02134028), a yellow fever outbreak in Brazil required administration of a live attenuated vaccine to at-risk individuals.

Objective

Our aim was to evaluate immune response to a live attenuated vaccine in the context of IL-4 receptor blockade (REGN1103, a dupilumab surrogate) in mice and in dupilumab-treated patients with moderate-to-severe asthma who participated in TRAVERSE.

Methods

In the preclinical study, mice were coadministered REGN1103/isotype control and live attenuated influenza vaccine/control, followed by influenza virus challenge. During TRAVERSE, 37 patients discontinued dupilumab treatment and were administered 17D live attenuated yellow fever vaccine (YFV). Safety and tolerability data, dupilumab serum concentrations, and plaque reduction neutralization titers before and after vaccination were collected.

Results

In the preclinical study, there was no impact of REGN1103 on vaccine efficacy in mice. In TRAVERSE, all 37 patients who received YFV achieved seroprotection despite most having therapeutic levels of dupilumab, with the magnitude of response appearing unrelated to prevaccination dupilumab concentrations. No instances of vaccine-related adverse events or vaccine hypersensitivity were reported in 36 patients; 1 patient reported nonserious body ache, malaise, and dizziness 7 days after vaccination but recovered fully.

Conclusion

The preclinical model suggested that dupilumab does not affect the efficacy of live attenuated influenza vaccine. The live attenuated YFV did not raise safety concerns and appeared to be well tolerated in patients with asthma who recently discontinued dupilumab treatment, and dupilumab concentrations had no apparent impact on immunologic response to the vaccine.

Hypersensitivity reactions to vaccines in children: from measles to SARS-CoV-2

Allergic individuals at risk for hypersensitivity reactions to measles vaccine marketed for a long time are well established. On the other hand, risk factors for hypersensitivity reactions to the new mRNA COVID-19 vaccines currently include a history of allergy, allergy to excipient of the vaccine, or hypersensitivity reactions to the first dose of COVID-19 vaccine. In the last two cases, the recipient should be assessed by an allergist before vaccination to share a decision on the choice of vaccination. Studies on skin testing accuracy and desensitization protocols to the COVID-19 vaccines and the efficacy of potential alternatives in patients with confirmed hypersensitivity reactions to the first COVID-19 vaccine are necessary to improve the safety of COVID-19 vaccines.

The fable of "The Doctor and the Goose," by Charles Chauvin Boisclair Deléry, D.M.P

Charles Chauvin Boisclair Deléry, D.M.P. - doctor of medicine of Paris, was perhaps the prototypical representative of Creole physicians, practising medicine in Louisiana in the 1800s, who were regarded as being equally proficient with pen, pills or pistols. This paper presents accounts of Deléry's yellow fever debate with Jean-Charles Faget, D.M.P., and their near duel, and his famous duel with Joseph Rouanet. Because of the personal and professional need to maintain honor, Rouanet may have challenged Deléry to a duel, not only because of vociferous disagreements between them over blood transfusion safety and efficacy, but due to Deléry's humiliation of Rouanet in his fable, "the Doctor and the Goose." We recovered the poem, transcribed and translated it, and discuss it as a device of witty rhetorical persuasion-a technique of the time used to belittle one's learned opponents. Fortunately, Deléry was not as equally proficient with pens and pistols, as both he and Rouanet survived the duel.