Limited specificity of commercially available SARS-CoV-2 IgG ELISAs in serum samples of African origin.

OBJECTIVES: Specific serological tests are mandatory for reliable SARS-CoV-2 diagnostics and seroprevalence studies. Here, we assess the specificities of four commercially available SARS-CoV-2 IgG ELISAs in serum/plasma panels originating from Africa, South America, and Europe. METHODS: 882 serum/plasma samples collected from symptom-free donors before the COVID-19 pandemic in three African countries (Ghana, Madagascar, Nigeria), Colombia, and Germany were analysed with three nucleocapsid-based ELISAs (Euroimmun Anti-SARS-CoV-2-NCP IgG, EDI™ Novel Coronavirus COVID-19 IgG, Mikrogen recomWell SARS-CoV-2 IgG), one spike/S1-based ELISA (Euroimmun Anti-SARS-CoV-2 IgG), and in-house common cold CoV ELISAs. RESULTS: High specificity was confirmed for all SARS-CoV-2 IgG ELISAs for Madagascan (93.4-99.4%), Colombian (97.8-100.0%), and German (95.9-100.0%) samples. In contrast, specificity was much lower for the Ghanaian and Nigerian serum panels (Ghana: NCP-based assays 77.7-89.7%, spike/S1-based assay 94.3%; Nigeria: NCP-based assays 39.3-82.7%, spike/S1-based assay 90.7%). 15 of 600 African sera were concordantly classified as positive in both the NCP-based and the spike/S1-based Euroimmun ELISA, but did not inhibit spike/ACE2 binding in a surrogate virus neutralisation test. IgG antibodies elicited by previous infections with common cold CoVs were found in all sample panels, including those from Madagascar, Colombia, and Germany and thus do not inevitably hamper assay specificity. Nevertheless, high levels of IgG antibodies interacting with OC43 NCP were found in all 15 SARS-CoV-2 NCP/spike/S1 ELISA positive sera. CONCLUSIONS: Depending on the chosen antigen and assay protocol, SARS-CoV-2 IgG ELISA specificity may be significantly reduced in certain populations probably due to interference of immune responses to endemic pathogens like other viruses or parasites.

Molecular and epidemiologic characterization of the diphtheria outbreak in Venezuela.

In 2016, Venezuela faced a large diphtheria outbreak that extended until 2019. Nasopharyngeal or oropharyngeal samples were prospectively collected from 51 suspected cases and retrospective data from 348 clinical records was retrieved from 14 hospitals between November 2017 and November 2018. Confirmed pathogenic Corynebactrium isolates were biotyped. Multilocus Sequence Typing (MLST) was performed followed by next-generation-based core genome-MLST and minimum spanning trees were generated. Subjects between 10 and 19 years of age were mostly affected (n = 95; 27.3%). Case fatality rates (CFR) were higher in males (19.4%), as compared to females (15.8%). The highest CFR (31.1%) was observed among those under 5, followed by the 40 to 49 age-group (25.0%). Nine samples corresponded to C. diphtheriae and 1 to C. ulcerans. Two Sequencing Types (ST), ST174 and ST697 (the latter not previously described) were identified among the eight C. diphtheriae isolates from Carabobo state. Cg-MLST revealed only one cluster also from Carabobo. The Whole Genome Sequencing analysis revealed that the outbreak seemed to be caused by different strains with C. diphtheriae and C. ulcerans coexisting. The reemergence and length of this outbreak suggest vaccination coverage problems and an inadequate control strategy.

Investigating the utility of Google trends for Zika and Chikungunya surveillance in Venezuela.

INTRODUCTION: Chikungunya and Zika Virus are vector-borne diseases responsible for a substantial disease burden in the Americas. Between 2013 and 2016, no cases of Chikungunya or Zika Virus were reported by the Venezuelan Ministry of Health. However, peaks of undiagnosed fever cases have been observed during the same period. In the context of scarce data, alternative surveillance methods are needed. Assuming that unusual peaks of acute fever cases correspond to the incidences of both diseases, this study aims to evaluate the use of Google Trends as an indicator of the epidemic behavior of Chikungunya and Zika. METHODS: Time-series cross-correlations of acute fever cases reported by the Venezuelan Ministry of Health and data on Google search queries related to Chikungunya and Zika were calculated. RESULTS: A temporal distinction has been made so that acute febrile cases occurring between 25th of June 2014 and 23rd of April 2015 were attributed to the Chikungunya virus, while cases occurring between 30th of April 2015 and 29th of April 2016 were ascribed to the Zika virus. The highest cross-correlations for each disease were shown at a lag of 0 (r = 0.784) for Chikungunya and at + 1 (r = 0.754) for Zika. CONCLUSION: The strong positive correlation between Google search queries and official data on acute febrile cases suggests that this resource can be used as an indicator of endemic urban arboviruses activity. In the Venezuelan context, Internet search queries might help to overcome some of the gaps that exist in the national surveillance system.

Therapeutic efficacy of artemether-lumefantrine for Plasmodium vivax infections in a prospective study in Guyana.

BACKGROUND: In Guyana, chloroquine + primaquine is used for the treatment of vivax malaria. A worldwide increase of chloroquine resistance in Plasmodium vivax led to questioning of the current malaria treatment guidelines. A therapeutic efficacy study was conducted using artemether-lumefantrine + primaquine against P. vivax to evaluate a treatment alternative for chloroquine. METHODS: From 2009 to 2010, a non-controlled study in two hospitals in Guyana was conducted. A total 61 patients with P. vivax infection were treated with artemether-lumefantrine as a six-dose regimen twice a day for three days with additional 0.25 mg/kg/d primaquine at day 0 for 14 days. Clinical and parasitological parameters were followed on days 0,1,2,3,7,14 and 28 in agreement with WHO guidelines. Plasmodium vivax DNA from eight patients was analysed for pvmdr1, molecular marker of resistance. RESULTS: Artemether-lumefantrine cleared 100% of parasites on day 1, but two patients (3%) had recurrence of parasites on day 28, suggesting relapse. No pvmdr1 Y976F polymorphism was detected. The treatment regimen was well tolerated. CONCLUSIONS: In Guyana, artemether-lumefantrine represents an adequate treatment option against P. vivax when combined with primaquine. Availability of this alternative will be of great importance in case of emerging chloroquine resistance against P. vivax.