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We evaluated the prevalence of Rift Valley fever virus IgG and IgM in human serum samples (n = 1,276) collected in 2013-2014 in northern Botswana. Our findings provide evidence of active circulation of this virus in humans in the absence of clinical disease in this region. [ABSTRACT FROM AUTHOR]

Background: Rift Valley fever virus (RVFV) remains heavily neglected in humans in Mozambique, even though recent outbreaks were reported in neighboring countries in humans and several cases of RVFV in cattle were reported in several districts in Mozambique. Findings: We conducted a cross sectional study during and after severe flooding that occurred in 2013 in Mozambique. Paired acute and convalescent serum samples were tested from febrile patients attending a primary health care unit in a suburban area of Maputo city for the presence of IgG and IgM antibodies against Rift Valley fever virus (RVFV) using enzyme-linked immunosorbent assay (ELISA). Seroconversion of IgG anti-RVFV was observed in 5 % (10/200) of convalescent patients and specific IgM anti-RVFV was detected in one acute patient (0.5 %; 1/200). All sera from acute patient tested negative by real time PCR. Conclusion: In conclusion, our results suggest that RVF represent an important but neglected cause of febrile illness following periods of flooding in southern Mozambique. [ABSTRACT FROM AUTHOR]

Rift Valley fever (RVF) is a viral zoonosis that primarily affects animals resulting in considerable economic losses due to death and abortions among infected livestock. RVF also affects humans with clinical symptoms ranging from an influenza-like illness to a hemorrhagic fever. Over the past years, RVF virus (RVFV) has caused severe outbreaks in livestock and humans throughout Africa and regions of the world previously regarded as free of the virus. This situation prompts the need to evaluate the diagnostic capacity and performance of laboratories worldwide. Diagnostic methods for RVFV detection include virus isolation, antigen and antibody detection methods, and nucleic acid amplification techniques. Molecular methods such as reverse-transcriptase polymerase chain reaction and other newly developed techniques allow for a rapid and accurate detection of RVFV. This study aims to assess the efficiency and accurateness of RVFV molecular diagnostic methods used by expert laboratories worldwide. Thirty expert laboratories from 16 countries received a panel of 14 samples which included RVFV preparations representing several genetic lineages, a specificity control and negative controls. In this study we present the results of the first international external quality assessment (EQA) for the molecular diagnosis of RVF. Optimal results were reported by 64% of the analyses, 21% of the analyses achieved acceptable results and 15% of the results revealed that there is need for improvement. Evenly good performances were achieved by specific protocols which can therefore be recommended as an accurate molecular protocol for the diagnosis of RVF. Other protocols showed uneven performances revealing the need for improved optimization and standardization of these protocols. [ABSTRACT FROM AUTHOR]

Abstract: An indirect enzyme-linked immunoassay (I-ELISA) based on the recombinant nucleocapsid protein (rNp) of Rift Valley fever virus was validated for the detection of specific IgG antibody in human sera. Validation data sets derived from testing sera collected in Africa (n =2967) were categorized according to the results of a virus neutralisation test. The assay had high intra- and inter-plate repeatability in routine runs. No detectable cross-reactions between IgG antibodies generated from mice experimentally infected with viruses representing genus Phlebovirus, Nairovirus, Orthobunyavirus and Bhanja virus of the family Bunyaviridae were observed. At a cut-off optimised by the two-graph receiver operating characteristics analysis at 95% accuracy level, the diagnostic sensitivity of the I-ELISA was 99.72% and diagnostic specificity 99.62% while estimates for the Youden''s index (J) and efficiency (Ef) were 0.993 and 99.62%. When cut-off values determined by mean plus two and by mean plus three standard deviations derived from I-ELISA readings in an uninfected reference population were used, the diagnostic sensitivity was 100% but estimates of Y, Ef and other combined measures of diagnostic accuracy were lower. The I-ELISA based on rNp is highly sensitive, specific and robust and can be applied for diagnosis of infection of Rift Valley fever and disease-surveillance studies in humans. [Copyright &y& Elsevier]

The mosquito-borne flavivirus, Kedougou virus (KEDV), first isolated in Senegal in 1972, is genetically related to dengue, Zika (ZIKV) and Spondweni viruses (SPOV). Serological surveillance studies in Senegal and isolation of KEDV in the Central African Republic indicate occurrence of KEDV infections in humans, but to date, no disease has been reported. Here, we assembled the coding-complete genome of a 1958 isolate of KEDV from a pool of Aedes circumluteolus mosquitoes collected in Ndumu, KwaZulu-Natal, South Africa. The AR1071 Ndumu KEDV isolate bears 80.51% pairwise nucleotide identity and 93.34% amino acid identity with the prototype DakAar-D1470 strain and was co-isolated with SPOV through intracerebral inoculation of suckling mice and passage on VeroE6 cells. This historical isolate expands the known geographic and temporal range of this relatively unknown flavivirus, aiding future temporal phylogenetic calibration and diagnostic assay refinement. [ABSTRACT FROM AUTHOR]

Dengue contributes a significant burden on global public health and economies. In Africa, the burden of dengue virus (DENV) infection is not well described. This review was undertaken to determine the prevalence of dengue and associated risk factors. A literature search was done on PubMed/MEDLINE, Scopus, Embase, and Google Scholar databases to identify articles published between 1960 and 2020. Meta-analysis was performed using a random-effect model at a 95% confidence interval, followed by subgroup meta-analysis to determine the overall prevalence. Between 1960 and 2020, 45 outbreaks were identified, of which 17 and 16 occurred in East and West Africa, respectively. Dengue virus serotype 1 (DENV-1) and DENV-2 were the dominant serotypes contributing to 60% of the epidemics. Of 2211 cases reported between 2009 and 2020; 1954 (88.4%) were reported during outbreaks. Overall, the prevalence of dengue was 29% (95% CI: 20–39%) and 3% (95% CI: 1–5%) during the outbreak and non-outbreak periods, respectively. Old age (6/21 studies), lack of mosquito control (6/21), urban residence (4/21), climate change (3/21), and recent history of travel (3/21) were the leading risk factors. This review reports a high burden of dengue and increased risk of severe disease in Africa. Our findings provide useful information for clinical practice and health policy decisions to implement effective interventions. [ABSTRACT FROM AUTHOR]

Rift Valley fever (RVF) is a re-emerging arboviral disease of public health and veterinary importance in Africa and the Arabian Peninsula. Major RVF epidemics were documented in South Africa in 1950–1951, 1974–1975, and 2010–2011. The number of individuals infected during these outbreaks has, however, not been accurately estimated. A total of 823 people in close occupational contact with livestock were interviewed and sampled over a six-month period in 2015–2016 within a 40,000 km2 study area encompassing parts of the Free State and Northern Cape provinces that were affected during the 2010–2011 outbreak. Seroprevalence of RVF virus (RVFV) was 9.1% (95% Confidence Interval (CI95%): 7.2–11.5%) in people working or residing on livestock or game farms and 8.0% in veterinary professionals. The highest seroprevalence (SP = 15.4%; CI95%: 11.4–20.3%) was detected in older age groups (≥40 years old) that had experienced more than one known large epidemic compared to the younger participants (SP = 4.3%; CI95%: 2.6–7.3%). The highest seroprevalence was in addition found in people who injected animals, collected blood samples (Odds ratio (OR) = 2.3; CI95%: 1.0–5.3), slaughtered animals (OR = 3.9; CI95%: 1.2–12.9) and consumed meat from an animal found dead (OR = 3.1; CI95%: 1.5–6.6), or worked on farms with dams for water storage (OR = 2.7; CI95%: 1.0–6.9). We estimated the number of historical RVFV infections of farm staff in the study area to be most likely 3849 and 95% credible interval between 2635 and 5374 based on seroprevalence of 9.1% and national census data. We conclude that human RVF cases were highly underdiagnosed and heterogeneously distributed. Improving precautions during injection, sample collection, slaughtering, and meat processing for consumption, and using personal protective equipment during outbreaks, could lower the risk of RVFV infection. [ABSTRACT FROM AUTHOR]

Abstract: Serodiagnosis of Rift Valley fever (RVF) currently relies on the use of live or inactivated whole virus as antigens. The recombinant nucleocapsid (N) protein of RVF virus was tested for diagnostic applicability in an indirect enzyme-linked immunosorbent assay (I-ELISA), using sera from experimentally infected sheep (n =128), vaccinated sheep (n =240), and field-collected sera from sheep (n =251), goats (n =362) and cattle (n =100). The N-protein based I-ELISA performed at least as good as VN and HI tests. In goat the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the I-ELISA was 100% when using the anti-species IgG conjugate. Using protein G as a detection system, the D-Sn and D-Sp in goats were 99.4% and 99.5%, in sheep field sera both 100%, in cattle 100% and 98.3%, respectively. The I-ELISA based on recombinant N-protein has the potential to complement the traditional assays for serodiagnosis of RVF. Advantages of the N-protein are its safety, stability and cost-effectiveness in use and production. [Copyright &y& Elsevier]

Abstract: This paper describes the cloning, sequencing and bacterial expression of the N protein of the Rift Valley fever virus (RVFV) ZIM688/78 isolate and its evaluation in indirect ELISAs (I-ELISA) for the detection of IgM and IgG antibodies in human and sheep sera. Sera used for the evaluation were from 106 laboratory workers immunised with an inactivated RVF vaccine, 16 RVF patients, 168 serial bleeds from 8 sheep experimentally infected with wild type RVFV and 210 serial bleeds from 10 sheep vaccinated with the live attenuated Smithburn RVFV strain. All human and animal sera that tested positive in the virus neutralisation test were also positive in the IgG I-ELISA. There was a high correlation (R 2 =0.8571) between virus neutralising titres and IgG I-ELISA readings in human vaccinees. In experimentally infected sheep IgG antibodies were detected from day 4 to 5 post-infection onwards and IgM antibodies from day 3 to 4. The IgG I-ELISA was more sensitive than virus neutralisation and haemagglutination-inhibition tests in detecting the early immune response in experimentally infected sheep. The I-ELISAs demonstrated that the IgG and IgM response to the Smithburn vaccine strain was slower and the levels of antibodies induced markedly lower than to wild type RVFV infection. [Copyright &y& Elsevier]