Development and validation of serological assays for viral hemorrhagic fevers and determination of the prevalence of Rift Valley fever in Borno State, Nigeria

Seromolecular survey and risk factor analysis of Crimean-Congo haemorrhagic fever orthonairovirus in occupationally exposed herdsmen and unexposed febrile patients in Kwara State, Nigeria

Crimean-Congo haemorrhagic fever virus (CCHFV) is a globally significant tick-borne zoonotic pathogen that causes fatal haemorrhagic disease in humans. Despite constituting an ongoing public health threat, limited research exists on the presence of CCHFV among herdsmen, an occupationally exposed population that has prolonged contact with ruminants and ticks. This cross-sectional study, conducted between October 2018 and February 2020 in Kwara State, Nigeria, was aimed at assessing CCHFV seroprevalence among herdsmen and non-herdsmen febrile patients, and identifying the associated risk factors. Blood samples from herdsmen (n = 91) and febrile patients in hospitals (n = 646) were analyzed for anti-CCHFV IgG antibodies and CCHFV S-segment RNA using ELISA and RT-PCR, respectively. Results revealed a remarkably high CCHFV seroprevalence of 92.3% (84/91) among herdsmen compared to 7.1% (46/646) in febrile patients. Occupational risk factors like animal and tick contact, tick bites, and hand crushing of ticks significantly contributed to higher seroprevalence in the herdsmen (p<0.0001). Herdsmen were 156.5 times more likely (p<0.0001) to be exposed to CCHFV than febrile patients. Notably, the odds of exposure were significantly higher (OR = 191.3; p<0.0001) in herdsmen with a history of tick bites. Although CCHFV genome was not detectable in the tested sera, our findings reveal that the virus is endemic among herdsmen in Kwara State, Nigeria. CCHFV should be considered as a probable cause of febrile illness among humans in the study area. Given the nomadic lifestyle of herdsmen, further investigations into CCHF epidemiology in this neglected population are crucial. This study enhances our understanding of CCHFV dynamics and emphasizes the need for targeted interventions in at-risk communities.

Seroprevalence of Rift Valley Fever virus in one-humped camels (Camelus dromedaries) in Egypt

Rift Valley fever (RVF) is a mosquito-borne viral disease that affects a variety of domestic animals, including cattle, sheep, goats, and camels, and has zoonotic potential. Although the rift valley fever virus (RVFV) is usually asymptomatic in camels, it can induce abortion in some pregnant animals. In the current study, a serosurvey was carried out to investigate the prevalence of RVFV antibodies and related risk factors in camels from four Egyptian governorates. A total of 400 serum samples were examined for anti-RVFV antibodies using a competitive enzyme-linked immunosorbent assay (c-ELISA). The results revealed that the overall prevalence of RVF among examined camels was 21.5% and the disease was more prevalent in Kafr ElSheikh governorate in Nile Delta of Egypt. In addition, the age group of camels with more than 5 years (OR=4.49, 95%CI: 1.39-14.49), the female sex (OR=3.38, 95%CI: 1.51-7.58), the emaciated animals (OR=1.52, 95%CI: 0.86-2.66), the summer season's infection (OR=5.98, 95%CI: 1.79-19.93), the presence of mosquitoes (OR= 2.88, 95%CI: 1.39-5.95), and the absence of mosquitoes control (OR=3.97, 95%CI: 2.09-7.57) were identified as risk factors for RVFV infection. The results of this study support knowledge on the risk factors for RVFV infection and demonstrate that camels raising in Egypt have RVFV antibodies. Quarantine measures or vaccination program should be implemented to reduce the likelihood of RVFV introduction, dissemination among susceptible animals, and ultimately transmission to humans.

Correlation between pseudotyped virus and authentic virus neutralisation assays, a systematic review and meta-analysis of the literature

Background

The virus neutralization assay is a principal method to assess the efficacy of antibodies in blocking viral entry. Due to biosafety handling requirements of viruses classified as hazard group 3 or 4, pseudotyped viruses can be used as a safer alternative. However, it is often queried how well the results derived from pseudotyped viruses correlate with authentic virus. This systematic review and meta-analysis was designed to comprehensively evaluate the correlation between the two assays.

Methods

Using PubMed and Google Scholar, reports that incorporated neutralisation assays with both pseudotyped virus, authentic virus, and the application of a mathematical formula to assess the relationship between the results, were selected for review. Our searches identified 67 reports, of which 22 underwent a three-level meta-analysis.

Results

The three-level meta-analysis revealed a high level of correlation between pseudotyped viruses and authentic viruses when used in an neutralisation assay. Reports that were not included in the meta-analysis also showed a high degree of correlation, with the exception of lentiviral-based pseudotyped Ebola viruses.

Conclusion

Pseudotyped viruses identified in this report can be used as a surrogate for authentic virus, though care must be taken in considering which pseudotype core to use when generating new uncharacterised pseudotyped viruses.

Contemporary epidemiological data of Rift Valley fever virus in humans, mosquitoes and other animal species in Africa: A systematic review and meta-analysis

Rift Valley fever (RVF) is a severe zoonotic mosquito-borne disease that represents an important threat to human and animal health, with major public health and socioeconomic impacts. This disease is endemic throughout many African countries and the Arabian Peninsula. This systematic review with meta-analysis was conducted to determine the RVF prevalence in humans, mosquitoes and other animal species in Africa. The review also provides contemporary data on RVF case fatality rate (CFR) in humans. In this systematic review with meta-analysis, a comprehensive literature search was conducted on the PubMed, Embase, Web of Science and Global Index Medicus databases from January 2000 to June 2022 to identify relevant studies. Pooled CFR and prevalence estimates were calculated using the random-effects model. Subgroup analysis and sensitivity analysis were performed, and the I2 -statistic was used to investigate a potential source of heterogeneity. A total of 205 articles were included in the final analysis. The overall RVF CFR in humans was found to be 27.5% [95% CI = 8.0-52.5]. The overall pooled prevalence was 7.8% [95% CI = 6.2-9.6] in humans and 9.3% [95% CI = 8.1-10.6] in animals, respectively. The RVF prevalence in individual mosquitoes ranged from 0.0% to 25%. Subgroup analysis showed substantial heterogeneity with respect to geographical regions and human categories. The study shows that there is a correspondingly similar prevalence of RVF in human and animals; however, human CFR is much higher than the observed prevalence. The lack of a surveillance programme and the fact that this virus has subclinical circulation in animals and humans could explain these observations. The implementation of a One Health approach for RVF surveillance and control would be of great interest for human and animal health.

Viral and Bacterial Zoonotic Agents in Dromedary Camels from Southern Tunisia: A Seroprevalence Study

The rapid spread of SARS-CoV-2 clearly demonstrated the potential of zoonotic diseases to cause severe harm to public health. Having limited access to medical care combined with severe underreporting and a lack of active surveillance, Africa carries a high burden of neglected zoonotic diseases. Therefore, the epidemiological monitoring of pathogen circulation is essential. Recently, we found extensive Middle East respiratory syndrome coronavirus (MERS-CoV) prevalence in free-roaming dromedary camels from southern Tunisia. In this study, we aimed to investigate the seroprevalence, and thus the risk posed to public health, of two additional viral and two bacterial pathogens in Tunisian dromedaries: Rift Valley fever virus (RVFV), foot-and-mouth disease virus (FMDV), Coxiella burnetii and Brucella spp. via ELISA. With 73.6% seropositivity, most animals had previously been exposed to the causative agent of Q fever, C. burnetii. Additionally, 7.4% and 1.0% of the dromedaries had antibodies against Brucella and RVFV, respectively, while no evidence was found for the occurrence of FMDV. Our studies revealed considerable immunological evidence of various pathogens within Tunisian dromedary camels. Since these animals have intense contact with humans, they pose a high risk of transmitting serious zoonotic diseases during active infection. The identification of appropriate countermeasures is therefore highly desirable.

Pseudotyped Vesicular Stomatitis Virus-Severe Acute Respiratory Syndrome-Coronavirus-2 Spike for the Study of Variants, Vaccines, and Therapeutics Against Coronavirus Disease 2019

World Health Organization (WHO) has prioritized the infectious emerging diseases such as Coronavirus Disease (COVID-19) in terms of research and development of effective tests, vaccines, antivirals, and other treatments. Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2), the etiological causative agent of COVID-19, is a virus belonging to risk group 3 that requires Biosafety Level (BSL)-3 laboratories and the corresponding facilities for handling. An alternative to these BSL-3/-4 laboratories is to use a pseudotyped virus that can be handled in a BSL-2 laboratory for study purposes. Recombinant Vesicular Stomatitis Virus (VSV) can be generated with complementary DNA from complete negative-stranded genomic RNA, with deleted G glycoprotein and, instead, incorporation of other fusion protein, like SARS-CoV-2 Spike (S protein). Accordingly, it is called pseudotyped VSV-SARS-CoV-2 S. In this review, we have described the generation of pseudotyped VSV with a focus on the optimization and application of pseudotyped VSV-SARS-CoV-2 S. The application of this pseudovirus has been addressed by its use in neutralizing antibody assays in order to evaluate a new vaccine, emergent SARS-CoV-2 variants (delta and omicron), and approved vaccine efficacy against variants of concern as well as in viral fusion-focused treatment analysis that can be performed under BSL-2 conditions.

Epidemiology of Crimean-Congo Hemorrhagic Fever (CCHF) in Africa-Underestimated for Decades

Crimean-Congo hemorrhagic fever (CCHF) is endemic in Africa, but the epidemiology remains to be defined. Using a broad database search, we reviewed the literature to better define CCHF evidence in Africa. We used a One Health approach to define the impact of CCHF by reviewing case reports, human and animal serology, and records of CCHF virus (CCHFV) isolations (1956-mid-2020). In addition, published and unpublished collection data were used to estimate the geographic distribution of Hyalomma ticks and infection vectors. We implemented a previously proposed classification scheme for organizing countries into five categories by the level of evidence. From January 1, 1956 to July 25, 2020, 494 CCHF cases (115 lethal) were reported in Africa. Since 2000, nine countries (Kenya, Mali, Mozambique, Nigeria, Senegal, Sierra Leone, South Sudan, Sudan, and Tunisia) have reported their first CCHF cases. Nineteen countries reported CCHF cases and were assigned level 1 or level 2 based on maturity of their surveillance system. Thirty countries with evidence of CCHFV circulation in the absence of CCHF cases were assigned level 3 or level 4. Twelve countries for which no data were available were assigned level 5. The goal of this review is to inform international organizations, local governments, and healthcare professionals about shortcomings in CCHF surveillance in Africa to assist in a movement toward strengthening policy to improve CCHF surveillance.

Epidemiology of Lassa Fever

Lassa fever (LF) is a lethal hemorrhagic disease primarily concentrated in the tropical savannah regions of Nigeria and the Mano River Union countries of Sierra Leone, Liberia, and Guinea. Endemic hotspots within these countries have had recurrent exposure to Lassa virus (LASV) via continual spillover from the host reservoir Mastomys natalensis. Increased trade and travel throughout the region have spread the virus to previously unexposed countries, including Ghana, Benin, Mali, and Côte d'Ivoire. In the absence of effective treatment or vaccines to LASV, preventative measures against Lassa fever rely heavily on reducing or eliminating rodent exposure, increasing the knowledge base surrounding the virus and disease in communities, and diminishing the stigmas faced by Lassa fever survivors.

Risk Factors for and Seroprevalence of Tickborne Zoonotic Diseases among Livestock Owners, Kazakhstan

Crimean-Congo hemorrhagic fever (CCHF), Q fever, and Lyme disease are endemic to southern Kazakhstan, but population-based serosurveys are lacking. We assessed risk factors and seroprevalence of these zoonoses and conducted surveys for CCHF-related knowledge, attitudes, and practices in the Zhambyl region of Kazakhstan. Weighted seroprevalence for CCHF among all participants was 1.2%, increasing to 3.4% in villages with a known history of CCHF circulation. Weighted seroprevalence was 2.4% for Lyme disease and 1.3% for Q fever. We found evidence of CCHF virus circulation in areas not known to harbor the virus. We noted that activities that put persons at high risk for zoonotic or tickborne disease also were risk factors for seropositivity. However, recognition of the role of livestock in disease transmission and use of personal protective equipment when performing high-risk activities were low among participants.

Systematic review and meta-analysis of the epidemiology of Lassa virus in humans, rodents and other mammals in sub-Saharan Africa

Accurate data on the Lassa virus (LASV) human case fatality rate (CFR) and the prevalence of LASV in humans, rodents and other mammals are needed for better planning of actions that will ultimately reduce the burden of LASV infection in sub-Saharan Africa. In this systematic review with meta-analysis, we searched PubMed, Scopus, Africa Journal Online, and African Index Medicus from 1969 to 2020 to obtain studies that reported enough data to calculate LASV infection CFR or prevalence. Study selection, data extraction, and risk of bias assessment were conducted independently. We extracted all measures of current, recent, and past infections with LASV. Prevalence and CFR estimates were pooled using a random-effect meta-analysis. Factors associated with CFR, prevalence, and sources of between-study heterogeneity were determined using subgroup and metaregression analyses. This review was registered with PROSPERO, CRD42020166465. We initially identified 1,399 records and finally retained 109 reports that contributed to 291 prevalence records from 25 countries. The overall CFR was 29.7% (22.3-37.5) in humans. Pooled prevalence of LASV infection was 8.7% (95% confidence interval: 6.8-10.8) in humans, 3.2% (1.9-4.6) in rodents, and 0.7% (0.0-2.3) in other mammals. Subgroup and metaregression analyses revealed a substantial statistical heterogeneity explained by higher prevalence in tissue organs, in case-control, in hospital outbreak, and surveys, in retrospective studies, in urban and hospital setting, in hospitalized patients, and in West African countries. This study suggests that LASV infections is an important cause of death in humans and that LASV are common in humans, rodents and other mammals in sub-Saharan Africa. These estimates highlight disparities between sub-regions, and population risk profiles. Western Africa, and specific key populations were identified as having higher LASV CFR and prevalence, hence, deserving more attention for cost-effective preventive interventions.

Prevalence of Crimean-Congo hemorrhagic fever virus in rural areas of Guinea

This article presents the results of a comprehensive survey of Guinea with the aim of assessing the burden of Crimean-Congo hemorrhagic fever virus (CCHFV) in rural areas of the country. Human serum samples (n = 2207) were studied using enzyme-linked immunosorbent assay (ELISA) for the presence of specific IgG against CCHFV. In addition, 4273 samples of partially- or fully-engorged ticks from several sources (cattle, domestic and roving dogs, and small mammals) were collected and studied using ELISA and RT-qPCR to detect CCHFV antigen and specific RNA. The data obtained show that 3.0 % of the population in rural Guinea was seropositive, without significant geographical or sexual differences. Seropositive individuals, however, were mainly in the 'active age' group (16-45 years old). Among ticks studied, the estimated prevalence of CCHFV was 1.3 ± 0.4 %. Five out of eight tick species studied were identified as CCHFV carriers in Guinea. Therefore, it can be assumed that the territory of Guinea is a single, continuous, natural focus of CCHFV. This identified medium intensity focus merits further study.

Diagnostic Testing for Crimean-Congo Hemorrhagic Fever

Crimean-Congo hemorrhagic fever is the most geographically widespread tick-borne virus, with infection resulting in mortality in up to 30% of cases. Clinical diagnosis alone is difficult due to the nonspecific nature of symptoms; therefore, laboratory diagnostics should be utilized for patients with residence in or travel to regions of endemicity in whom the disease is suspected. This minireview provides an overview of laboratory tests available for Crimean-Congo hemorrhagic fever (CCHF) and their utility in diagnosis with a focus on diagnosing CCHF in humans.

Crimean-Congo hemorrhagic fever (CCHF) seroprevalence: A systematic review and meta-analysis

Crimean-Congo haemorrhagic fever (CCHF) is the most widespread, tick-borne viral disease affecting humans and therefore this paper performed a meta-analysis to highlight seroprevalence features of CCHF in a global context. After a preliminary review of the 396 papers representing areas throughout the world, 206 were selected for detailed meta-analysis. In general the total means of CCHF seroprevalence were, respectively 4.7 and 24.6% for humans and animals; and 17.1, 18.9, 24.3, 29.3 and 27.1% for camels, cattle, goats, sheep and livestock. Statistical analysis revealed a significant difference in seroprevalence between humans and camels (P = 0.043), cattle (P = 0.010), goats (P = 0.015), sheep (P = 0.005) and livestock (P = 0.017). Regionally, there also was a difference between humans, and goats (P = 0.0001), sheep (P = 0.007) and livestock (P = 0.002). Globally, CCHF seroprevalence in at-risk professionals was 7.5 fold greater than in normal humans, while CCHF seroprevalence was 5 fold greater in animals, camels, cattle, goats, sheep and livestock than normal humans. Animal contact, animal husbandry, farming, tick bite history and secretion exposure were the most frequently reported CCHF seropositivity risk factors. This study serves as an important resource for epidemiological discussions related to CCHF and CCHF seroprevalence features, providing specific information in understanding human and animal mean and trend CCHF seroprevalence for different regions of the world and on an aggregate global scale; seroprevalence in at-risk professionals; and total mean and trend CCHF seropositivity involving risk factors.

Sensitivity and specificity of diagnostic tests for Lassa fever: a systematic review

BACKGROUND

Lassa fever virus has been enlisted as a priority pathogen of epidemic potential by the World Health organization Research and Development (WHO R & D) Blueprint. Diagnostics play a crucial role in epidemic preparedness. This systematic review was conducted to determine the sensitivity and specificity of Lassa fever diagnostic tests for humans.

METHODS

We searched OVID Medline, OVID Embase, Scopus and Web of Science for laboratory based and field studies that reported the performance of diagnostic tests for Lassa fever in humans from 1 January 1990 to 25 January 2019. Two reviewers independently screened all the studies and included only studies that involved the evaluation of a Lassa fever diagnostic test and provided data on the sensitivity and specificity. The quality of the studies was assessed using the QUADAS-2 criteria. Data on the study location, study design, type of sample, index test, reference tests and diagnostic performance were extracted from the studies.

RESULTS

Out of a total of 1947 records identified, 1245 non-duplicate citations were obtained. Twenty-six (26) full-text articles examined which identified 08 studies meeting pre-defined criteria. Only one study was a field evaluation study. The sensitivity and specificity of the point of care (RDT) against the Nikisins qPCR were 91.2%(95% CI:75.2-97.7) and 86%(95% CI: 71.4-94.2) at temperatures 18-30 °C, while the sensitivity and specificity of the single IgM ELISA assay against standard RT-PCR were 31.1%(95%CI: 25.6-37) and 95.7%(95%CI:92.8-97.7). The sensitivity of the combined ELISA Antigen/IgM assay(against virus isolation), the recombinant IgM/IgG ELISA(against standard RT-PCR), and the IgM/IgG immunoblot(against IFA) were 88%(95%CI:77-95), 25.9%(95%CI:20.8-31.6), and 90.7%(95%CI:84.13-97.27) respectively. The specificity of the combined ELISA Antigen/IgM assay(against virus isolation), the recombinant IgM/IgG ELISA(against standard RT-PCR), and the IgM/IgG immunoblot(against IFA) were 90%(95%CI:88-91), 100%(95%CI:98.2-100), and 96.3%(95%CI:92.2-100) respectively.

CONCLUSION

Lassa fever has assays for antigenaemia, IgM, IgG and PCR detection. The RDT reportedly performed well but more data are needed from other countries and at temperatures above 30 °C. Most combined immunoassays perform better than the single IgM. Multiplex and pan-Lassa assays are needed. More well conducted field studies are needed.

TRIAL REGISTRATION

Prospero registration number: CRD42018091585 .

Rift valley fever virus infection among livestock handlers in Ibadan, Nigeria

Livestock handlers are occupationally exposed to Rift Valley fever virus (RVFV) because of frequent and longer contact with mosquito vectors, animal blood and other tissues. We determined the seroprevalence of RVF virus infection among livestock handlers in Ibadan, Nigeria. Blood samples were collected from 265 workers in two major livestock markets and a livestock farm. Questionnaires were administered to obtain information on risk factors that may be associated with RVF virus transmission. The blood samples were tested using enzyme-linked immunosorbent assays (ELISA) to detect multispecies anti-RVF virus IgG/IgM and human anti-RVF virus IgM. In total, 14 (5.3%) of the 265 participants tested positive for anti-RVFV IgG. Seropositive individuals were more among livestock keepers (5.6%) than butchers (3.6%). Workers that frequently visited the livestock rearing areas of the northern part of Nigeria had a statistically significant (P = 0.004) higher rate of infection compared to those that did not. Very few (0.8%) of these workers knew about RVF virus while none had been vaccinated against the virus infection. This study indicates that RVF virus continues to circulate sub-clinically in Nigeria, thus the need to educate and vaccinate individuals who are occupationally at risk of infection.

Endemic and emerging arboviral diseases of livestock in Nigeria: a review

Arthropod-borne viruses (arboviruses) are the largest biologic group of vertebrate viruses and constitute important emerging infectious disease agents globally. Arthropod transmission provides a way for viruses to cross species barriers since the same arthropod may bite animals that rarely or never come into close contact in nature. In Nigeria, arboviruses have, over several decades, caused severe diseases in livestock resulting in great economic losses and, sometimes, infection of humans leading to morbidity and mortality. In the present review, a computerized search of existing literature was conducted using the Google search engine and PubMed electronic database to identify and review relevant publications on arboviral diseases of livestock in Nigeria. The keywords used were 'arbovirus', 'arthropod-borne viral diseases' or 'livestock diseases' and 'Nigeria' while the Boolean operator 'OR' was used to combine and narrow the searches. Additional information was obtained by searching the veterinary libraries for journals not listed in the database. The available publications were thereafter reviewed and findings qualitatively described. Our findings revealed that although there were several studies on arboviruses and the livestock diseases they cause in Nigeria, most of such reports were made four to six decades ago, with only a few reported recently. Consequently, the true economic and public health impact of these diseases are likely to be underestimated, mainly due to under-reporting or lack of awareness of them. Thus, it is essential to update information on arboviral diseases in Nigeria in order to increase awareness of the diseases and facilitate their prompt identification and reporting. The importance of routine surveillance for arbovirus livestock diseases and sentinel herd monitoring as basis for development of an early warning and alert system to prevent future outbreaks is discussed.

Isolation, Characterization, and Phylogenetic Analysis of Two New Crimean-Congo Hemorrhagic Fever Virus Strains from the Northern Region of Xinjiang Province, China

Crimean-Congo hemorrhagic fever (CCHF) caused by the CCHF virus (CCHFV) is a tick-borne natural focal disease with a mortality rate of approximately 50%. CCHFV is widely prevalent in Africa, southern Asia, the Middle East, and southeast Europe. CCHF outbreaks have been reported previously in Xinjiang province, China, especially in its southern region. Epidemiological surveys conducted on ticks and animals have revealed the presence of CCHFV strains in ticks, rodents, and infected individuals from cities and counties in southern Xinjiang. Phylogenetic analyses revealed that the Chinese CCHFV strains belong to one genotype, based on complete sequences of the S segments of its negative-stranded RNA genome. The present study reports two new CCHFV strains isolated from Hyalomma asiaticum asiaticum ticks collected from Fukang City and Wujiaqu City in the northern region of Xinjiang. Viral characteristics and their evolutionary relationships were analyzed through metagenomic and reverse-transcription PCR analyses; these analyses indicated that the genotype of both strains was different from that of other Chinese strains. Furthermore, previous reports of CCHFV in Xinjiang were reviewed and phylogenetic analyses were performed. CCHFV was found to prevail in Fukang City in Junggar Basin for more than 20 years, and that Fukang City and Wujiaqu City are considered natural reservoirs of different genotypes of CCHFV strains. Our findings facilitate the understanding of CCHFV distribution in Xinjiang province and provide insights into the evolutionary relationships among Chinese CCHFV strains.

Serological and Virological Evidence of Crimean-Congo Haemorrhagic Fever Virus Circulation in the Human Population of Borno State, Northeastern Nigeria

Background

Despite several studies on the seroprevalence of antibodies against Crimean-Congo Haemorrhagic Fever virus (CCHFV) from humans and cattle in Nigeria, detailed investigation looking at IgG and IgM have not been reported. Additionally, there have been no confirmed cases of human CCHFV infection reported from Nigeria.

Principal Findings

Samples from sera (n = 1189) collected from four Local Government Areas in Borno State (Askira/Uba, Damboa, Jere and Maiduguri) were assessed for the presence of IgG and IgM antibodies. The positivity rates for IgG and IgM were 10.6% and 3.5%, respectively. Additionally, sera from undiagnosed febrile patients (n = 380) were assessed by RT-PCR assay for the presence of CCHFV RNA. One positive sample was characterised by further by next generation sequencing (NGS) resulting in complete S, M and L segment sequences.

Conclusions

This article provides evidence for the continued exposure of the human population of Nigeria to CCHFV. The genomic analysis provides the first published evidence of a human case of CCHFV in Nigeria and its phylogenetic context.

Crimean-Congo haemorrhagic fever (CCHF) is an acute tick-borne zoonotic disease. The causative agent, CCHF virus (CCHFV), has the most extensive geographical distribution of the medically important tick-borne viral diseases with a distribution over much of Asia, the Middle East, Africa and expanding areas of south-eastern Europe. Whilst the main route of human infection with CCHFV is predominantly through tick bite, it can also be spread via bodily fluids and it has a reputation for causing nosocomial outbreaks in healthcare settings. Whilst CCHFV has been identified in ticks from Nigeria since 1970, there is scarce information on human infection. Within this report, the prevalence of CCHFV-reactive antibodies has been assessed in human sera providing evidence of continued circulation of the virus in the human population of Borno state, Nigeria. Additionally, in one sample the presence of viral RNA was detected which allowed a full sequence of the CCHFV to be obtained. This is the first report of CCHFV being associated in a human case from Nigeria and the full genetic characterisation of the virus being completed. The evidence within supports the hypothesis that CCHFV is endemic in Nigeria and should be considered as an aetiological agent in febrile patients.

Characterization of Glycoprotein-Mediated Entry of Severe Fever with Thrombocytopenia Syndrome Virus

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging hemorrhagic fever with a high case fatality rate caused by SFTS virus (SFTSV). Effective vaccines and specific therapies for SFTS are urgently sought, and investigation into virus-host cell interactions is expected to contribute to the development of antiviral strategies. In this study, we have developed a pseudotype vesicular stomatitis virus (VSV) bearing the unmodified Gn/Gc glycoproteins (GPs) of SFTSV (SFTSVpv). We have analyzed the host cell entry of this pseudotype virus and native SFTSV. Both SFTSVpv and SFTSV exhibited high infectivity in various mammalian cell lines. The use of lysosomotropic agents indicated that virus entry occurred via pH-dependent endocytosis. SFTSVpv and SFTSV infectivity was neutralized by serial dilutions of convalescent-phase patient sera. Entry of SFTSVpv and growth of SFTSV were increased in Raji cells expressing not only the C-type lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) but also DC-SIGN-related (DC-SIGNR) and liver and lymph node sinusoidal endothelial cell C-type lectin (LSECtin). 25-Hydroxycholesterol (25HC), a soluble oxysterol metabolite, inhibited the cell entry of SFTSVpv and the membrane fusion of SFTSV. These results indicate that pH-dependent endocytosis of SFTSVpv and SFTSV is enhanced by attachment to certain C-type lectins. SFTSVpv is an appropriate model for the investigation of SFTSV-GP-mediated cell entry and virus neutralization at lower biosafety levels. Furthermore, 25HC may represent a potential antiviral agent against SFTS.

IMPORTANCE

SFTSV is a recently discovered bunyavirus associated with SFTS, a viral hemorrhagic fever with a high case fatality rate endemic to China, South Korea, and Japan. Because little is known about the characteristics of the envelope protein and entry mechanisms of SFTSV, further studies will be required for the development of a vaccine or effective therapies. In this study, we investigated the mechanism of SFTSV cell entry using SFTSVpv and the native virus. SFTSV can grow in nonsusceptible cell lines in the presence of certain C-type lectins. Moreover, 25HC, an oxysterol metabolite, may represent a potential therapeutic inhibitor of SFTSV infection.

Serologic assays for the detection and strain identification of Pteropine orthoreovirus

Pteropine orthoreovirus (PRV), potentially of bat origin, is reported to be a causative agent of emerging respiratory tract infections among humans in Southeast Asia. We evaluated the efficacy of serologic assays using the major outer capsid and cell attachment proteins (CAP) of PRV strains in the screening, confirmation and identification of three groups of human PRV infections; Indonesian/Japanese, Indonesian/Hong Kong and Malaysian strains. The different serologic assays were tested using rabbit polyclonal antisera raised against these proteins of selected PRV strains, and validation was carried out using sera from a Miyazaki-Bali/2007 PRV-infected patient and the patient's contacts. The results of this study showed that rabbit polyclonal antisera raised against the CAP of the Miyazaki-Bali/2007 PRV strain showed the highest reactivity to the Miyazaki-Bali/2007 PRV and to a lesser extent, cross-reactivity with the HK23629/07 and Melaka PRVs, respectively. Neutralization activity against the Miyazaki-Bali/2007 PRV was observed using rabbit anti-Miyazaki-Bali/2007 PRV CAP (320) but not with rabbit anti-HK23629/07 (<20) and Melaka (<20) PRV CAP. This lack of cross-neutralization, suggests the potential for human reinfection with different strains. The use of sera collected from contacts of the Miyazaki-Bali/2007 PRV-infected patient suggested that human-to-human infections with PRV are unlikely. Previously reported cases of PRV infections among human have been mild. However, the expanding geographic distribution of these viruses, of which its virulence remains unknown, warrants close monitoring to enable the development of prevention and control strategies in the event that a change in virulence occurs.

Serologic evidence of exposure to Rift Valley fever virus detected in Tunisia

Rift Valley fever virus (RVFv) is capable of causing dramatic outbreaks amongst economically important animal species and is capable of causing severe symptoms and mortality in humans. RVFv is known to circulate widely throughout East Africa; serologic evidence of exposure has also been found in some northern African countries, including Mauritania. This study aimed to ascertain whether RVFv is circulating in regions beyond its known geographic range. Samples from febrile patients (n = 181) and nonfebrile healthy agricultural and slaughterhouse workers (n = 38) were collected during the summer of 2014 and surveyed for exposure to RVFv by both serologic tests and PCR. Of the 219 samples tested, 7.8% of nonfebrile participants showed immunoglobulin G reactivity to RVFv nucleoprotein and 8.3% of febrile patients showed immunoglobulin M reactivity, with the latter samples indicating recent exposure to the virus. Our results suggest an active circulation of RVFv and evidence of human exposure in the population of Tunisia.

Viral Hemorrhagic Fever Diagnostics

There are 4 families of viruses that cause viral hemorrhagic fever (VHF), including Filoviridae. Ebola virus is one virus within the family Filoviridae and the cause of the current outbreak of VHF in West Africa. VHF-endemic areas are found throughout the world, yet traditional diagnosis of VHF has been performed in large reference laboratories centered in Europe and the United States. The large amount of capital needed, as well as highly trained and skilled personnel, has limited the availability of diagnostics in endemic areas except in conjunction with governmental and nongovernmental entities. However, rapid diagnosis of VHF is essential to efforts that will limit outbreaks. In addition, increased global travel suggests VHF diagnoses may be made outside of the endemic areas. Thus, understanding how to diagnose VHF is imperative for laboratories worldwide. This article reviews traditional and current diagnostic modalities for VHF.

Inability of rat DPP4 to allow MERS-CoV infection revealed by using a VSV pseudotype bearing truncated MERS-CoV spike protein

Middle East respiratory syndrome (MERS) coronavirus (Co-V) contains a single spike (S) protein, which binds to a receptor molecule, dipeptidyl peptidase 4 (DPP4; also known as CD26), and serves as a neutralizing antigen. Pseudotyped viruses are useful for measuring neutralization titers against highly infectious viruses as well as for studying their mechanism of entry. In this study, we constructed a series of cytoplasmic deletion mutants of MERS-CoV S and compared the efficiency with which they formed pseudotypes with vesicular stomatitis virus. A pseudotype bearing an S protein with the C-terminal 16 amino acids deleted (MERSpv-St16) reached a maximum titer that was approximately tenfold higher than that of a pseudotype bearing a non-truncated full-length S protein. Using MERSpv-St16, we demonstrated the inability of rat DPP4 to serve as a functional receptor for MERS-CoV, suggesting that rats are not susceptible to MERS-CoV infection. This study provides novel information that enhances our understanding of the host range of MERS-CoV.