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Moutchia J, Njouom R, Rumpler E, Besombes C, Texier G, Tejiokem M, Crépey P, Fontanet A, Shimakawa Y. Maternal age at first childbirth and geographical variation in HBV prevalence in Cameroon: Important role of mother-to-child transmission. Clin Infect Dis 2021; 74:836-845. [PMID: 34125878 DOI: 10.1093/cid/ciab548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND The prevalence of hepatitis B virus (HBV) infection varies geographically around the world. However, the underlying reasons for this variation are unknown. Using a nationally representative population-based sample from all 58 administrative divisions in Cameroon, we examined the association between median maternal age at first childbirth in a preceding generation, a proxy for the frequency of mother-to-child transmission (MTCT) of HBV in a region, and the risk of chronic HBV infection, defined as positive surface antigen (HBsAg), in the index generation. METHODS We estimated a division-specific median maternal age at first childbirth using historical data from Demographic Health Surveys (DHS) in 1991/1998/2004/2011. We tested HBsAg in 2011 DHS participants. We used maps to display spatial variation and spatial models for the analysis. RESULTS In 14,150 participants (median 27 years old, 51% females), the overall weighted prevalence of HBsAg was 11.9% (95%CI: 11.0-12.8), with a wide geographical variation across the divisions (range: 6.3-23.7%). After adjusting for confounding factors and spatial dependency, lower maternal age at first childbirth was significantly associated with positive HBsAg at the division level (β: 1.89 [95%CI: 1.26-2.52], p<0.001), and at the individual level (OR: 1.20 [95%CI: 1.04-1.39], p=0.016). A similar ecological correlation was observed across other African countries. CONCLUSIONS The significant association between the maternal age at first childbirth and HBsAg-positivity suggests a crucial role of MTCT in maintaining high HBV endemicity in some areas in Cameroon. This underlines an urgent need to effectively prevent MTCT in order to achieve WHO's global hepatitis elimination goals.
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Affiliation(s)
- Jude Moutchia
- Unité d'Épidémiologie des Maladies Émergentes, Institut Pasteur, Paris, France.,REPERES « Recherche en Pharmaco-Epidémiologie et Recours aux Soins » - EA 7449, Université Rennes, Ecole des Hautes Etudes en Santé Publique, Rennes, France
| | - Richard Njouom
- Department of Virology, Centre Pasteur du Cameroun, Yaoundé, Cameroon
| | - Eva Rumpler
- Unité d'Épidémiologie des Maladies Émergentes, Institut Pasteur, Paris, France
| | - Camille Besombes
- Unité d'Épidémiologie des Maladies Émergentes, Institut Pasteur, Paris, France
| | - Gaëtan Texier
- Department of Epidemiology and Public Health, Centre Pasteur du Cameroun, Yaoundé, Cameroon.,Aix Marseille University, IRD, AP-HM, SSA, VITROME, IHU Méditerranée Infection, Marseille, France
| | - Mathurin Tejiokem
- Department of Epidemiology and Public Health, Centre Pasteur du Cameroun, Yaoundé, Cameroon
| | - Pascal Crépey
- REPERES « Recherche en Pharmaco-Epidémiologie et Recours aux Soins » - EA 7449, Université Rennes, Ecole des Hautes Etudes en Santé Publique, Rennes, France
| | - Arnaud Fontanet
- Unité d'Épidémiologie des Maladies Émergentes, Institut Pasteur, Paris, France.,PACRI unit, Conservatoire National des Arts et Métiers, Paris, France
| | - Yusuke Shimakawa
- Unité d'Épidémiologie des Maladies Émergentes, Institut Pasteur, Paris, France
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Tan M, Bhadoria AS, Cui F, Tan A, Van Holten J, Easterbrook P, Ford N, Han Q, Lu Y, Bulterys M, Hutin Y. Estimating the proportion of people with chronic hepatitis B virus infection eligible for hepatitis B antiviral treatment worldwide: a systematic review and meta-analysis. Lancet Gastroenterol Hepatol 2020; 6:106-119. [PMID: 33197397 PMCID: PMC7801814 DOI: 10.1016/s2468-1253(20)30307-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 09/08/2020] [Accepted: 09/17/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND In 2016, of the estimated 257 million people living with chronic hepatitis B virus (HBV) infection worldwide, only a small proportion was diagnosed and treated. The insufficiency of information on the proportion of people infected with HBV who are eligible for treatment limits the interpretation of global treatment coverage. We aimed to estimate the proportion of people with chronic HBV infection who were eligible for antiviral treatment worldwide, based on the WHO 2015 guidelines. METHODS In this systematic review and meta-analysis, we searched Medline, EMBASE, and the Cochrane databases from Jan 1, 2007, to Jan 31, 2018, for studies describing HBsAg-positive people in the population or health-care facilities. We extracted information from published studies using a standardised form to estimate the frequency of cirrhosis, abnormal alanine aminotransferase (ALT), HBV DNA exceeding 2000 IU/mL or 20 000 IU/mL, presence of HBeAg, and eligibility for treatment as per WHO and other guidelines as reported in the studies. We pooled proportions through meta-analysis with random effects. The study was registered with PROSPERO, CRD42020132345. FINDINGS Of the 13 497 studies, 162 were eligible and included in our analysis. These studies included 145 789 participants. The pooled estimate of the proportion of cirrhosis was 9% (95% CI 8-10), ranging from 6% (4-8) in community settings to 10% (9-11) in clinic settings. Examining the proportion of participants who had characteristics used to determine eligibility in the WHO guidelines, 1750 (10·1%) of 17 394 had HBV DNA exceeding 20 000 IU/mL, and 20 425 (30·8%) of 66 235 had ALT above the upper limit of normal. 32 studies reported eligibility for treatment according to WHO or any other guidelines, with a pooled estimate of eligibility at 19% (95% CI 18-20), ranging from 12% (6-18) for studies in community settings to 25% (19-30) in clinic settings. INTERPRETATION Many studies described people with HBV infection, but few reported information in a way that allowed assessment of eligibility for treatment. Although about one in ten of the 257 million people with HBV infection (26 million) might be in urgent need of treatment because of cirrhosis, a larger proportion (12-25%) is eligible for treatment in accordance with different guidelines. Future studies describing people with HBV infection should report on treatment eligibility, according to broadly agreed definitions. FUNDING WHO and US Centers for Disease Control and Prevention.
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Affiliation(s)
- Mingjuan Tan
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland; Department of Medicine, National University Health System, Singapore
| | - Ajeet S Bhadoria
- All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Fuqiang Cui
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland
| | | | - Judith Van Holten
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland
| | | | - Nathan Ford
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland
| | - Qin Han
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland
| | - Ying Lu
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland
| | - Marc Bulterys
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland
| | - Yvan Hutin
- Department of HIV/AIDS and Global Hepatitis Programme, WHO, Geneva, Switzerland.
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3
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Boyce CL, Willis S, Archampong TNA, Lartey M, Sagoe KW, Obo-Akwa A, Kenu E, Kwara A, Blackard JT. Identification of hepatitis B virus genotype A/E recombinants in Ghana. Virus Genes 2019; 55:707-712. [PMID: 31346975 PMCID: PMC6750976 DOI: 10.1007/s11262-019-01690-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 07/19/2019] [Indexed: 10/26/2022]
Abstract
Hepatitis B virus (HBV) exhibits a high degree of heterogeneity with at least 10 genotypes (A-J) identified to date. Intergenotypic recombination is relatively common. Previously, we investigated HBV drug resistance in HIV/HBV co-infected individuals in Ghana. After identifying multiple circulating genotypes and a novel D/E recombinant, we sought to determine if additional individuals were also infected with recombinant HBV. Partial genome sequences from three individuals were initially identified as genotype A4. Full-length HBV genomes were obtained using rolling circle amplification followed by PCR and shown to cluster with known A/E recombinant viruses. Similar recombination breakpoints were observed in these three individuals suggesting local spread of this novel recombinant HBV in Ghana.
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Affiliation(s)
- Ceejay L Boyce
- Division of Digestive Disease, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Stephaney Willis
- Division of Digestive Disease, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Timothy N A Archampong
- Department of Medicine and Therapeutics, School of Medicine and Dentistry, College of Health Sciences, University of Ghana, Accra, Ghana
- Korle-Bu Teaching Hospital, Accra, Ghana
| | - Margaret Lartey
- Department of Medicine and Therapeutics, School of Medicine and Dentistry, College of Health Sciences, University of Ghana, Accra, Ghana
- Korle-Bu Teaching Hospital, Accra, Ghana
| | - Kwamena W Sagoe
- Department of Medical Microbiology, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Adjoa Obo-Akwa
- Department of Medicine and Therapeutics, School of Medicine and Dentistry, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Ernest Kenu
- Korle-Bu Teaching Hospital, Accra, Ghana
- School of Public Health, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Awewura Kwara
- Division of Infectious Diseases and Global Medicine, University of Florida, Gainesville, FL, USA
| | - Jason T Blackard
- Division of Digestive Disease, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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4
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Boyce CL, Ganova-Raeva L, Archampong TNA, Lartey M, Sagoe KW, Obo-Akwa A, Kenu E, Kwara A, Blackard JT. Identification and comparative analysis of hepatitis B virus genotype D/E recombinants in Africa. Virus Genes 2017; 53:538-547. [PMID: 28567562 PMCID: PMC5710801 DOI: 10.1007/s11262-017-1469-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 05/25/2017] [Indexed: 12/17/2022]
Abstract
Globally, there are approximately 240 million people chronically infected with hepatitis B virus (HBV)-a major cause of hepatocellular carcinoma. Ten different HBV genotypes (A-J) have been identified with distinct geographic distributions. Novel variants generated by recombination between different HBV genotypes have been documented worldwide and represent an important element of genetic variability with possible clinical implications. Here, the complete genome sequence of an HBV genotype D/E recombinant from Ghana is reported. The full-length sequence was obtained using rolling circle amplification followed by PCR and sequenced using next-generation sequencing (NGS). A consensus sequence was extracted from the NGS data and underwent phylogenetic analysis to determine genotype, as well as the recombination pattern. Subsequently, the sequence was compared to recombinants described previously in Africa. Based on MCMC phylogenetic analysis, SimPlot recombination analyses, and intragroup genetic distance, the isolate 007N full-length genome is unique compared to other reported D/E recombinants in Africa.
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Affiliation(s)
- Ceejay L Boyce
- Division of Digestive Disease, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Lilia Ganova-Raeva
- Division of Viral Hepatitis, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Timothy N A Archampong
- Department of Medicine and Therapeutics, School of Medicine and Dentistry, College of Health Sciences, University of Ghana, Accra, Ghana
- Korle-Bu Teaching Hospital, Accra, Ghana
| | - Margaret Lartey
- Department of Medicine and Therapeutics, School of Medicine and Dentistry, College of Health Sciences, University of Ghana, Accra, Ghana
- Korle-Bu Teaching Hospital, Accra, Ghana
| | - Kwamena W Sagoe
- Department of Medical Microbiology, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Adjoa Obo-Akwa
- Department of Medicine and Therapeutics, School of Medicine and Dentistry, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Ernest Kenu
- Korle-Bu Teaching Hospital, Accra, Ghana
- School of Public Health, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Awewura Kwara
- Warren Alpert Medical School of Brown University, Providence, RI, USA
- The Miriam Hospital, Providence, RI, USA
- Division of Infectious Diseases and Global Medicine, University of Florida, Gainesville, FL, USA
| | - Jason T Blackard
- Division of Digestive Disease, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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Bigna JJ, Amougou MA, Asangbeh SL, Kenne AM, Noumegni SRN, Ngo-Malabo ET, Noubiap JJ. Seroprevalence of hepatitis B virus infection in Cameroon: a systematic review and meta-analysis. BMJ Open 2017; 7:e015298. [PMID: 28667212 PMCID: PMC5734365 DOI: 10.1136/bmjopen-2016-015298] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
OBJECTIVE Better knowledge of hepatitis B virus (HBV) infection prevalence at the national level can help to implement pertinent strategies to address HBV related burden. The aim was to estimate the seroprevalence of HBV infection in Cameroon. DESIGN Systematic review and meta-analysis. PARTICIPANTS People residing in Cameroon. DATA SOURCES Electronic databases including PubMed/MEDLINE, African Journals Online (AJOL), ScienceDirect, WHO-Afro Library, WHO-IRIS, African Index Medicus, National Institute of Statistics and National AIDS Control Committee, Cameroon; regardless of language and from 1 January 2000 to 30 September 2016. This was completed with a manual search of references of relevant papers. Risk of bias in methodology of studies was measured using the Newcastle-Ottawa Scale. RESULTS Out of 511 retrieved papers, 44 studies with a total of 105 603 individuals were finally included. The overall pooled seroprevalence was 11.2% (95% CI 9.7% to 12.8%) with high heterogeneity between studies (I2=97.9%). Egger's test showed no publication bias (p=0.167). A sensitivity analysis excluding individuals at high risk of HBV infection and after adjustment using trim and fill method showed a pooled seroprevalence of 10.6% (95% CI 8.6% to 12.6%) among 100 501 individuals (general population, blood donors and pregnant women). Sources of heterogeneity included geographical regions across country and setting (rural 13.3% vs urban 9.0%), and implementation of HBV universal immunisation (born after 9.2% vs born before 0.7%). Sex, site, timing of data collection, HBV screening tools and methodological quality of studies were not sources of heterogeneity. LIMITATION Only a third of the studies had low risk of bias in their methodology. CONCLUSION The seroprevalence of HBV infection in Cameroon is high. Effective strategies to interrupt the transmission of HBV are urgently required. Specific attention is needed for rural settings, certain regions and people born before the implementation of the HBV universal immunisation programme in Cameroon in 2005. REGISTRATION PROSPERO, CRD42016042654.
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Affiliation(s)
- Jean Joel Bigna
- Department of Epidemiology and Public Health, Centre Pasteur of Cameroon, Yaoundé, Cameroon
- School of Public Health, Faculty of Medicine, University of Paris Sud XI, Le Kremlin Bicêtre, France
| | - Marie A Amougou
- Department of Virology, Centre Pasteur of Cameroon, Yaoundé, Cameroon
- Faculty of Sciences, University of Yaoundé 1, Yaoundé, Cameroon
| | - Serra Lem Asangbeh
- Agence Nationale de Recherche sur le SIDA et les Hépatites Virales (ANRS), Yaoundé, Cameroon
| | - Angeladine Malaha Kenne
- Department of Epidemiology and Public Health, Centre Pasteur of Cameroon, Yaoundé, Cameroon
| | - Steve Raoul N Noumegni
- School of Public Health, Faculty of Medicine, University of Paris Sud XI, Le Kremlin Bicêtre, France
- Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon
| | - Elodie T Ngo-Malabo
- Department of Virology, Centre Pasteur of Cameroon, Yaoundé, Cameroon
- Faculty of Sciences, University of Yaoundé 1, Yaoundé, Cameroon
| | - Jean Jacques Noubiap
- Department of Medicine, Groote Schuur Hospital and University of Cape Town, Cape Town, South Africa
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Rodgers MA, Vallari AS, Harris B, Yamaguchi J, Holzmayer V, Forberg K, Berg MG, Kenmenge J, Ngansop C, Awazi B, Mbanya D, Kaptue L, Brennan C, Cloherty G, Ndembi N. Identification of rare HIV-1 Group N, HBV AE, and HTLV-3 strains in rural South Cameroon. Virology 2017; 504:141-151. [PMID: 28193549 DOI: 10.1016/j.virol.2017.01.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 02/07/2023]
Abstract
Surveillance of emerging viral variants is critical to ensuring that blood screening and diagnostic tests detect all infections regardless of strain or geographic location. In this study, we conducted serological and molecular surveillance to monitor the prevalence and diversity of HIV, HBV, and HTLV in South Cameroon. The prevalence of HIV was 8.53%, HBV was 10.45%, and HTLV was 1.04% amongst study participants. Molecular characterization of 555 HIV-1 specimens identified incredible diversity, including 7 subtypes, 12 CRFs, 6 unclassified, 24 Group O and 2 Group N infections. Amongst 401 HBV sequences were found a rare HBV AE recombinant and two emerging sub-genotype A strains. In addition to HTLV-1 and HTLV-2 strains, sequencing confirmed the fifth known HTLV-3 infection to date. Continued HIV/HBV/HTLV surveillance and vigilance for newly emerging strains in South Cameroon will be essential to ensure diagnostic tests and research stay a step ahead of these rapidly evolving viruses.
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Affiliation(s)
| | | | - B Harris
- Abbott Laboratories, Abbott Park, IL, USA
| | | | | | - K Forberg
- Abbott Laboratories, Abbott Park, IL, USA
| | - M G Berg
- Abbott Laboratories, Abbott Park, IL, USA
| | - J Kenmenge
- Université de Yaoundé I, Yaoundé, Cameroon
| | - C Ngansop
- Université de Yaoundé I, Yaoundé, Cameroon
| | - B Awazi
- Université de Yaoundé I, Yaoundé, Cameroon
| | - D Mbanya
- Université de Yaoundé I, Yaoundé, Cameroon
| | - L Kaptue
- Université des Montagnes, Montagnes, Bangangté, Cameroon
| | - C Brennan
- Abbott Laboratories, Abbott Park, IL, USA
| | - G Cloherty
- Abbott Laboratories, Abbott Park, IL, USA
| | - N Ndembi
- Institute of Human Virology Nigeria, Abuja, Nigeria
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Magoro T, Gachara G, Mavhandu L, Lum E, Kimbi HK, Ndip RN, Bessong P. Serologic and genotypic characterization of hepatitis B virus in HIV-1 infected patients from South West and Littoral Regions of Cameroon. Virol J 2016; 13:178. [PMID: 27769271 PMCID: PMC5073451 DOI: 10.1186/s12985-016-0636-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 10/12/2016] [Indexed: 12/19/2022] Open
Abstract
Background HBV and HIV share similar transmission routes. Concurrent infection with the two viruses usually results in more severe and progressive liver disease, and a higher incidence of cirrhosis, liver cancer and mortality. Further, this co-infection may lead to cross-resistance between HIV and HBV drugs and increased liver injury, either due to direct hepatotoxicity or drug-related immune-reconstitution hepatitis. These challenges necessitate continuous surveillance for HBV among HIV infected individuals to guide patient management. We conducted this study to understand the serologic and genotypic characteristics of HBV among HIV/HBV infected patients in South West and Littoral Regions of Cameroon. Methods Plasma samples were screened for HBsAg, HBeAg, Anti-HBs and anti-HBc using ELISA followed by DNA extraction from all HBsAg positive samples. A 366 bp region covering the overlapping surface/polymerase gene was amplified by a nested PCR and the product sequenced using Big Dye sequencing chemistry. The resulting sequences were then analyzed for genotypes and both escape and drug resistance mutations. Results Of the 455 samples in this study, 25.5 % (n = 116) were HBsAg positive and 46 of these had their DNA successfully amplified. Genotype E was found in 32 samples (69.6 %) and genotype A in the rest of the samples. Escape mutations associated with failure of diagnosis (Y100C, R122K and Q129H) and with vaccine escape (Q129R and T131N) were detected in varying frequencies in the population. Polymerase mutations implicated in resistance to lamivudine and other ʟ-nucleoside analogues were detected in seven patients (15.2 %), while all the samples lacked mutations associated with resistance to adefovir and tenofovir. Conclusions These findings suggest the endemicity of HBV and the predominance of genotypes A and E in the study population. Also, drug resistance findings support the use of tenofovir based ART regimens among HIV/HBV co-infected persons. There is need for continuous HBV screening and monitoring in HIV infected individuals in these regions.
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Affiliation(s)
- Tshifhiwa Magoro
- HIV/AIDS & Global Health Research Program, Department of Microbiology, University of Venda, Private bag X5050, Thohoyandou, 0950, Limpopo, South Africa
| | - George Gachara
- HIV/AIDS & Global Health Research Program, Department of Microbiology, University of Venda, Private bag X5050, Thohoyandou, 0950, Limpopo, South Africa.,Department of Medical Laboratory Sciences, Kenyatta University, Nairobi, Kenya
| | - Lufuno Mavhandu
- HIV/AIDS & Global Health Research Program, Department of Microbiology, University of Venda, Private bag X5050, Thohoyandou, 0950, Limpopo, South Africa
| | - Emmaculate Lum
- Department of Zoology and Animal Physiology, Faculty of Science, University of Buea, Buea, Cameroon.,Department of Biological Sciences, Higher Teachers' Training College, University of Yaounde, Yaoundé, Cameroon
| | - Helen K Kimbi
- Department of Zoology and Animal Physiology, Faculty of Science, University of Buea, Buea, Cameroon.,Department of Medical Laboratory Science, Faculty of Health Sciences, University of Bamenda, Bamenda, Bambili, Cameroon
| | - Roland N Ndip
- Department of Biochemistry and Microbiology, Faculty of Science and Agriculture, University of Fort Hare, Alice, South Africa.,Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Pascal Bessong
- HIV/AIDS & Global Health Research Program, Department of Microbiology, University of Venda, Private bag X5050, Thohoyandou, 0950, Limpopo, South Africa.
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