Molecular surveillance for dengue serotypes among the population living in Moyen-Ogooué province, Gabon; evidence of the presence of dengue serotype 1.

BACKGROUND: Despite dengue virus (DENV) outbreak in Gabon a decade ago, less is known on the potential circulation of DENV serotypes in the country. Previous studies conducted in some areas of the country, are limited to hospital-based surveys which reported the presence of some cases of serotype 2 and 3 seven years ago and more recently the serotype 1. As further investigation, we extend the survey to the community of Moyen Ogooué region with the aim to assess the presence of the dengue virus serotypes, additionally to characterize chikungunya (CHIKV) infection and describe the symptomatology associated with infections. METHOD: A cross-sectional survey was conducted from April 2020 to March 2021. The study included participants of both sexes and any age one year and above, with fever or history of fever in the past seven days until blood collection. Eligible volunteers were clinically examined, and blood sample was collected for the detection of DENV and CHIKV using RT-qPCR. Positive samples were selected for the target sequencing. RESULTS: A total of 579 volunteers were included. Their mean age (SD) was 20 (20) years with 55% of them being female. Four cases of DENV infection were diagnosed giving a prevalence of 0.7% (95%CI: 0.2-1.8) in our cohort while no case of CHIKV was detected. The common symptoms and signs presented by the DENV cases included fatigue, arthralgia myalgia, cough, and loss of appetite. DENV-1was the only virus detected by RT-qPCR. CONCLUSION: Our results confirm the presence of active dengue infection in the region, particularly DENV-1, and could suggest the decline of DENV-2 and DENV-3. Continuous surveillance remains paramount to comprehensively describe the extent of dengue serotypes distribution in the Moyen-Ogooué region of Gabon.

Genetic Diversity and Detection of Respiratory Viruses Excluding SARS-CoV-2 during the COVID-19 Pandemic in Gabon, 2020-2021.

Acute respiratory infections are a major global burden in resource-limited countries, including countries in Africa. Although COVID-19 has been well studied since the pandemic emerged in Gabon, Central Africa, less attention has been paid to other respiratory viral diseases, and very little data are available. Herein, we provide the first data on the genetic diversity and detection of 18 major respiratory viruses in Gabon during the COVID-19 pandemic. Of 582 nasopharyngeal swab specimens collected from March 2020 to July 2021, which were SARS-CoV-2 negative, 156 were positive (26%) for the following viruses: enterovirus (20.3%), human rhinovirus (HRV) (4.6%), human coronavirus OC43 (1.2%), human adenovirus (0.9%), human metapneumovirus (hMPV) (0.5%), influenza A virus (IAV) (0.3%), and human parainfluenza viruses (0.5%). To determine the genetic diversity and transmission route of the viruses, phylogenetic analyses were performed using genome sequences of the detected viruses. The IAV strain detected in this study was genetically similar to strains isolated in the USA, whereas the hMPV strain belonging to the A2b subtype formed a cluster with Kenyan strains. This study provides the first complete genomic sequences of HRV, IAV, and hMPV detected in Gabon, and provides insight into the circulation of respiratory viruses in the country.

Genetic Diversity of Hepatitis B and C Viruses Revealed by Continuous Surveillance from 2015 to 2021 in Gabon, Central Africa.

Viral hepatitis remains one of the largest public health concerns worldwide. Especially in Central Africa, information on hepatitis virus infections has been limited, although the prevalence in this region has been reported to be higher than the global average. To reveal the current status of hepatitis B and C virus (HBV and HCV) infections and the genetic diversity of the viruses, we conducted longitudinal surveillance in Gabon. We detected 22 HBV and 9 HCV infections in 2047 patients with febrile illness. Genetic analyses of HBV identified subgenotype A1 for the first time in Gabon and an insertion generating a frameshift to create an X-preC/C fusion protein. We also revealed that most of the detected HCVs belonged to the "Gabon-specific" HCV subtype 4e (HCV-4e), and the entire nucleotide sequence of the HCV-4e polyprotein was determined to establish the first reference sequence. The HCV-4e strains possessed resistance-associated substitutions similar to those of other HCV-4 strains, indicating that the use of direct-acting antiviral therapy may be complex. These results provide a better understanding of the current situation of hepatitis B and C virus infections in Central Africa and will help public health organizations develop effective countermeasures to eliminate chronic viral hepatitis in this region.

Long-term validation of a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for the rapid detection of SARS-CoV-2 from March 2020 to October 2021 in Central Africa, Gabon.

BACKGROUND: Despite the development of several methods for diagnosing COVID-19, long-term validation of such methods remains limited. In the early phase of the COVID-19 pandemic, we developed a rapid and sensitive diagnostic method based on reverse transcription loop-mediated isothermal amplification (RT-LAMP) methodology, which is suitable for point-of-care application or for use in resource-limited settings to detect SARS-CoV-2. To assess the applicability of the RT-LAMP assay technique to resource-limited regions, such as rural areas in Africa, and to verify the usability of the method against various SARS-CoV-2 variants, the method was validated using clinical samples collected longitudinally during the pandemic. METHODOLOGY/PRINCIPAL FINDINGS: First, the sensitivity of the RT-LAMP assay for detecting 10 SARS-CoV-2 variants was evaluated using viral RNA samples extracted from cell culture with a portable battery-supported device, resulting in the successful detection of 20-50 copies of the viral genome within 15 min, regardless of the variant. COVID-19 positive samples collected in Gabon between March 2020 and October 2021 were used to evaluate the sensitivity of the assay and to calculate the copy number of the SARS-CoV-2 genome. More than 292 copies of the viral genome were detected with 100% probability within 15 min in almost all tests. CONCLUSIONS: This long-term validation study clearly demonstrated the applicability of the RT-LAMP assay for the clinical diagnosis of COVID-19 in resource-limited settings of Africa, such as rural areas in Gabon. The results show the potential of the assay as a promising COVID-19 diagnostic method, especially in rural and remote regions located far from the official diagnosis facilities in urban or semi-urban areas.

Re-emergence of dengue, chikungunya, and Zika viruses in 2021 after a 10-year gap in Gabon.

Mosquito-borne viral infections are a major concern in endemic areas, such as Africa. Although outbreaks have been reported throughout Africa, only a few surveillance studies have been conducted in Gabon since the outbreaks of dengue virus (DENV) and chikungunya virus (CHIKV) in 2010. Therefore, the current situation is unknown. This study aimed to investigate the presence of arboviruses, especially DENV (serotypes 1-4), CHIKV, and Zika virus (ZIKV), in Gabon, Central Africa. Between 2020 and 2021, we collected 1060 serum samples from febrile patients and screened them against viruses using reverse transcription-quantitative PCR. We detected two DENV serotypes 1 (DENV-1), one CHIKV, and one ZIKV, and subsequently analyzed the genome sequences. To determine the genetic diversity and transmission route of the viruses, phylogenetic analysis was performed using complete or partial genome sequences. The DENV-1 and CHIKV strains detected in this study were closely related to the previous Gabonese strains, whereas the recent ZIKV strain was genetically different from a strain detected in 2007 in Gabon. This study provides new genomic information on DENV-1, CHIKV, and ZIKV that were detected in Gabon and insight into the circulation of the viruses in the country and their introduction from neighboring African countries.

Unrecognized introduction of SARS-CoV-2 variants of concern to Central Africa: Import and local transmission of B.1.1.7 in Gabon in the very early stage of the variant spread to the African continent.

The rapid spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant of concern with higher infectivity has already resulted in the enormous increase in infection cases worldwide. We report an unrecognized introduction of the variant B.1.1.7 in Gabon in December 2020, which was the initial phase of the variant introduction to Africa. The B.1.1.7 variant was also detected in a hospitalized patient in January 2021, indicating a rapid spread of the variant in Gabon since its first detection. Phylogenetic analysis revealed that the detected B.1.1.7 variants originated from the distinct regions, strongly suggesting that the B.1.1.7 variant had been repeatedly introduced to Gabon since December 2020. These results provide insights on the unrecognized risks of infections with variants of concern, and show the necessity to conduct continuous genomic monitoring for immediate alert and control of novel SARS-CoV-2 variant infections.