Richard Njouom - Academia.edu (original) (raw)

Papers by Richard Njouom

Journal of Epidemiology and Global Health

Over a period of about 9 months, we conducted three serosurveys in the two major cities of Camero... more Over a period of about 9 months, we conducted three serosurveys in the two major cities of Cameroon to determine the prevalence of SARS-COV-2 antibodies and to identify factors associated with seropositivity in each survey. We conducted three independent cross-sectional serosurveys of adult blood donors at the Central Hospital in Yaoundé (CHY), the Jamot Hospital in Yaoundé (JHY) and at the Laquintinie Hospital in Douala (LHD) who consented in writing to participate. Before blood sampling, a short questionnaire was administered to participants to collect their sociodemographic and clinical characteristics. We included a total of 743, 1202, and 1501 participants in the first (January 25–February 15, 2021), second (May 03–28, 2021), and third (November 29–December 31, 2021) surveys, respectively. The adjusted seroprevalence increased from 66.3% (95% CrI 61.1–71.3) in the first survey to 87.2% (95% CrI 84.0–90.0) in the second survey, and 98.4% (95% CrI 96.8–99.7) in the third survey. ...

Additional file 1: Table S1. Search strategy in PubMed. Table S2. Risk of bias tool. Table S3. Ri... more Additional file 1: Table S1. Search strategy in PubMed. Table S2. Risk of bias tool. Table S3. Risk of bias on study investigating the association between HEV infection and maternofetal outcomes. Table S4. Individual characteristics of studies included in the meta-analysis prevalence of HEV infection in the global population of pregnant women. Table S5. Individual characteristics of studies included in the meta-analysis of pregnancy outcomes in HEV infection in the global population of pregnant women. Table S6. Characteristics of studies included in the meta-analysis. Figure S1. The review process. Figure S2. Funnel plot for HEV prevalence in asymptomatic pregnant women. Figure S3. Funnel plot for HEV prevalence in symptomatic pregnant women.

Table S2. Summary Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age gro... more Table S2. Summary Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age groups and influenza viruses by categories of country ageing index. The Global Influenza B Study, 1999-2014. Table S3. Summary Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age groups and influenza viruses by percentage of outpatients among cases reported to the influenza surveillance system. The Global Influenza B Study, 1999-2014. Table S4. Summary Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age groups and influenza viruses by country latitude. The Global Influenza B Study, 1999-2014. Table S5. Summary Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age groups and influenza viruses by percentage of influenza cases caused by that influenza virus in the same season. The Global Influenza B Study, 1999-2014. Table S6. Summary Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age groups and infl...

Clinical Infectious Diseases, 2021

Background The prevalence of hepatitis B virus (HBV) infection varies geographically around the w... more Background The prevalence of hepatitis B virus (HBV) infection varies geographically around the world. Yet, its underlying mechanisms 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 Demographic Health Surveys (DHSs) conducted in 1991, 1998, 2004, and 2011. We tested HBsAg in 2011 DHS participants. We used maps to display spatial variation. Results In 14 150 participants (median age, 27 years; 51% females), the overall weighted prevalence of HBsAg was 11.9% (95% confidence interval [CI], 11.0 to 12.8), with a wide geographical variatio...

Additional file 1. Microphotographs of the A: (H&E × 10) liver parenchyma within the limits of no... more Additional file 1. Microphotographs of the A: (H&E × 10) liver parenchyma within the limits of normal but showing a slight dilation of sinusoids; B: (H&E × 10) and C: (H&E × 20) chronic hepatitis with moderate activity characterized by ballonnisation, cellular clarification of moderate intensity and the presence of macrovascular steatosis less than 20%; the morphological variants of HCC. D: (H&E × 4) and E: (H&E × 20) Moderately differentiated HCC with trabecular/acinar pattern; F: Moderately differentiated HCC with moderately to severe steatosis pattern (H&E × 40). H&E Hematin-Eosin.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific ... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et a ̀ la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

PLOS ONE, 2021

Introduction Meta-analyses conducted so far on the association between diabetes mellitus (DM) and... more Introduction Meta-analyses conducted so far on the association between diabetes mellitus (DM) and the tuberculosis (TB) development risk did not sufficiently take confounders into account in their estimates. The objective of this systematic review was to determine whether DM is associated with an increased risk of developing TB with a sensitivity analyses incorporating a wider range of confounders including age, gender, alcohol consumption, smoke exposure, and other comorbidities. Methods Pubmed, Embase, Web of Science and Global Index Medicus were queried from inception until October 2020. Without any restriction to time of study, geographical location, and DM and TB diagnosis approaches, all observational studies that presented data for associations between DM and TB were included. Studies with no abstract or complete text, duplicates, and studies with wrong designs (review, case report, case series, comment on an article, and editorial) or populations were excluded. The odds rati...

BMC Research Notes, 2018

Objective: Dried blood spots (DBS) offer multiple benefits for collecting, storing and shipping w... more Objective: Dried blood spots (DBS) offer multiple benefits for collecting, storing and shipping whole blood samples. Our objective was to compare, for the first time in Africa, the performance of DBS with respect to plasma in the detection of Hepatitis B surface antigen (HBsAg) and antibodies to Hepatitis C Virus (anti-HCV) using Architect, Abbott Diagnostics. Results: DBS had a sensitivity of 99%, a specificity of 100%, a positive predictive value of 99%, a negative predictive value of 100% and a kappa index of 0.99 for the detection of HBsAg. For anti-HCV detection, the sensitivity, specificity, positive predictive value, negative predictive value and kappa index were 99%, 98%, 98%, 99%, and 0.97, respectively. This study confirms that DBS may be a reliable alternative specimen type for HBV and HCV diagnosis.

Journal of Virological Methods, 2017

According to the WHO/UNAIDS recommendations, an acceptable HIV rapid diagnostic tests (RDTs) has ... more According to the WHO/UNAIDS recommendations, an acceptable HIV rapid diagnostic tests (RDTs) has to perform a sensitivity≥99% and a specificity≥98%. Given the constant release of new RDTs for HIV testing in the market and the high HIV genetic diversity in Cameroon, it is interesting to monitor their performances in that setting. A total of 240 HIV positive (including 219 HIV-1 M, 15 HIV-1 O, 1 HIV-1 N, 1 HIV-1 M/O recombinant and 4 HIV-2) and 240 HIV negative plasma samples were used to evaluate twelve routinely used RDTs in Cameroon. A reference algorithm combining Enzyme Immunoassays and nucleic acid testing was used as gold standard. The sensitivity, specificity, positive predictive value, and negative predictive value of the twelve RDTs evaluated varied between 93.7 and 100%; 95.8 and 100%; 96.0 and 100%, and 94.1 and 100%, respectively. Five out of the twelve RDTs could not detect some HIV-1 O variants, one of them failed to detect an HIV-2 variant while all them efficiently detected HIV-1 N and HIV M/O recombinant. Our findings underscore the need to monitor the performances of RDTs to be used for HIV testing in Cameroon using locally obtained well-characterized samples panels.

BMC Infectious Diseases, 2015

Background: Hepatitis B is a major health concern in Africa. The vaccine against hepatitis B viru... more Background: Hepatitis B is a major health concern in Africa. The vaccine against hepatitis B virus (HBV) was introduced into the Expanded Programme on Immunization (EPI) of Cameroon and Senegal in 2005, and of CAR (Central African Republic) in 2008. A cross-sectional study was conducted to assess HBV immunization coverage following the vaccine's introduction into the EPI and factors associated with having been vaccinated. Methods: All hospitalized children, regardless of the reasons for their hospitalization, between 3 months and 6 years of age, for whom a blood test was scheduled during their stay and whose condition allowed for an additional 2 mL blood sample to be taken, and who provided the parent's written consent were included. All children anti-HBs-and anti-HBc + were tested for HBsAg. Vaccination coverage was assessed in three different ways: immunization card, maternal recall and serologic anti-HBs profile. Results: 1783 children were enrolled between April 2009 and May 2010. An immunization card was only available for 24 % of the children. The median age was 21 months. Overall HBV immunization coverage based on immunization cards was 99 %, 49 % and 100 % in Cameroon, CAR and Senegal, respectively (p < 0,001). The immunization rate based on maternal recall was 91 %, 17 % and 88 % in Cameroon, CAR and Senegal, respectively (p < 0,001). According to serology (anti-HBs titer ≥ 10 mUI/mL and anti-HBc-), the coverage rate was 68 %, 13 % and 46 % in Cameroon, CAR and Senegal, respectively (p < 0,001). In Senegal and Cameroon, factors associated with having been vaccinated were: mother's higher education (OR = 2.2; 95 % CI [1.5-3.2]), no malnutrition (OR = 1.6; 95 % CI [1.1-2.2]), access to flushing toilets (OR = 1.6; 95 % CI [1.1-2.3]), and < 24 months old (OR = 2.1; 95 % CI [1.3-3.4] between 12 and 23 months and OR = 2.7; 95 % CI [1.6-4.4] < 12 months). The prevalence of HBV-infected children (HBsAg+) were 0.7 %, 5.1 %, and 0.2 % in Cameroon, CAR and Senegal, respectively (p < 0.001). Conclusions: Assessing immunization coverage based on immunization cards, maternal recall or administrative data could be usefully reinforced by epidemiological data combined with immunological profiles. Serology-based studies should be implemented regularly in African countries, as recommended by the WHO. Malnutrition, lack of maternal education and poverty are factors associated with vaccine non-compliance. The countries' vaccination programs should actively address these problems.

BMC Research Notes, 2014

Background: Dog rabies is endemic in most African countries and the risk of human rabies is estim... more Background: Dog rabies is endemic in most African countries and the risk of human rabies is estimated to be high in Cameroon according to WHO estimations in 2010. This study aimed to describe the circulation rabies virus (RABV) among dogs in the southern regions of Cameroon from 2010 to 2013 in a context, where mass vaccination campaigns are launched annually in order to control rabies in domestic animals including dogs and cats. Findings: From 2010 to 2013, 93 animal specimens (dogs: 91, monkey: 1, pig: 1) originating from the southern regions of Cameroon were collected and tested for rabies virus at the Centre Pasteur of Cameroon by fluorescent antibody test (FAT) and virus isolation. Of the total dog specimens, 69.2% (63/91) originated from the central part of the southern regions and 50.5% (46/91) were from the capital city Yaounde. Overall, 74.2% (66/89) of dogs' specimens that could be tested were found rabies-positive while specimens from the monkey and pig were tested negative. Overall, dog rabies was repeatedly detected in the southern regions of Cameroon especially in the nation capital, Yaounde even though low specimen submission and geographic bias did not permit major conclusions about its actual rate, geographical and over time distribution. Conclusions: The results of this study indicate that rabies is endemic in the dog population which is of public health concern. Therefore, coordinated rabies control program should be conducted to reduce the rabies incidence in dogs and in humans. In addition, proper rabies surveillance program including reporting system should be established to monitor the success of the control program in Cameroon.

World Journal of Hepatology, 2021

BACKGROUND The hepatitis B virus (HBV) infection is a global public health concern that affects a... more BACKGROUND The hepatitis B virus (HBV) infection is a global public health concern that affects about 2 billion people and causes 1 million people deaths yearly. HBV is a blood-borne disease and healthcare workers (HCWs) are a high-risk group because of occupational hazard to patients’ blood. Different regions of the world show a highly variable proportion of HCWs infected and/or immunized against HBV. Global data on serologic markers of HBV infection and immunization in HCWs are very important to improve strategies for HBV control. AIM To determine the worldwide prevalence of HBV serological markers among HCWs. METHODS In this systematic review and meta–analyses, we searched PubMed and Excerpta Medica Database (Embase) to identify studies published between 1970 and 2019 on the prevalence of HBV serological markers in HCWs worldwide. We also manually searched for references of relevant articles. Four independent investigators selected studies and included those on the prevalence of each of the HBV serological markers including hepatitis B surface antigen (HBsAg), hepatitis e antigen (HBeAg), immunoglobulin M anti-HBc, and anti-HBs. Methodological quality of eligible studies was assessed and random-effect model meta-analysis resulted in the pooled prevalence of HBV serological markers HBV infection in HCWs. Heterogeneity (I²) was assessed using the χ² test on Cochran’s Q statistic and H parameters. Heterogeneity’ sources were explored through subgroup and metaregression analyses. This study is registered with PROSPERO, number CRD42019137144. RESULTS We reviewed 14059 references, out of which 227 studies corresponding to 448 prevalence data among HCWs (224936 HCWs recruited from 1964 to 2019 in 71 countries) were included in this meta-analysis. The pooled seroprevalences of current HBsAg, current HBeAg, and acute HBV infection among HCWs were 2.3% [95% confidence interval (CI): 1.9-2.7], 0.2% (95%CI: 0.0-1.7), and 5.3% (95%CI: 1.4-11.2), respectively. The pooled seroprevalences of total immunity against HBV and immunity acquired by natural HBV infection in HCWs were 56.6% (95%CI: 48.7-63.4) and 9.2% (95%CI: 6.8-11.8), respectively. HBV infection was more prevalent in HCWs in low-income countries, particularly in Africa. The highest immunization rates against HBV in HCWs were recorded in urban areas and in high-income countries including Europe, the Eastern Mediterranean and the Western Pacific. CONCLUSION New strategies are needed to improve awareness, training, screening, vaccination, post-exposure management and treatment of HBV infection in HCWs, and particularly in low-income regions.

Viruses

SARS-CoV-2 is constantly evolving with lineages emerging and others eclipsing. Some lineages have... more SARS-CoV-2 is constantly evolving with lineages emerging and others eclipsing. Some lineages have an important epidemiological impact and are known as variants of interest (VOIs), variants under monitoring (VUMs) or variants of concern (VOCs). Lineage A.27 was first defined as a VUM since it holds mutations of concern. Here, we report additional lineage A.27 data and sequences from five African countries and describe the molecular characteristics, and the genetic history of this lineage worldwide. Based on the new sequences investigated, the most recent ancestor (tMRCA) of lineage A.27 was estimated to be from April 2020 from Niger. It then spread to Europe and other parts of the world with a peak observed between February and April 2021. The detection rate of A.27 then decreased with only a few cases reported during summer 2021. The phylogenetic analysis revealed many sub-lineages. Among them, one was defined by the substitution Q677H in the spike (S) gene, one was defined by the s...

SSRN Electronic Journal, 2020

Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

PLOS Neglected Tropical Diseases, 2020

Viruses

Some say that small is beautiful, and if beauty could be measured by levels of diversity and comp... more Some say that small is beautiful, and if beauty could be measured by levels of diversity and complexity, we could definitely say that viruses are beautiful [...]

PLOS Neglected Tropical Diseases

There are uncertainties about the global epidemiological data of infections due to Crimean-Congo ... more There are uncertainties about the global epidemiological data of infections due to Crimean-Congo hemorrhagic fever virus (CCHFV). We estimated the global case fatality rate (CFR) of CCHFV infections and the prevalence of CCHFV in humans, ticks and other animal species. We also explored the socio-demographic and clinical factors that influence these parameters. In this systematic review with meta–analyses we searched publications from database inception to 03rd February 2020 in Pubmed, Scopus, and Global Index Medicus. Studies included in this review provided cross-sectional data on the CFR and/or prevalence of one or more targets used for the detection of CCHFV. Two independent investigators selected studies to be included. Data extraction and risk of bias assessment were conducted independently by all authors. Data collected were analysed using a random effect meta-analysis. In all, 2345 records were found and a total of 312 articles (802 prevalence and/or CFR data) that met the in...

PLOS Neglected Tropical Diseases

A substantial amount of epidemiological data has been reported on Enterovirus D68 (EV-D68) infect... more A substantial amount of epidemiological data has been reported on Enterovirus D68 (EV-D68) infections after the 2014 outbreak. Our goal was to map the case fatality rate (CFR) and prevalence of current and past EV-D68 infections. We conducted a systematic review (PROSPERO, CRD42021229255) with published articles on EV-68 infections in PubMed, Embase, Web of Science and Global Index Medicus up to January 2021. We determined prevalences using a model random effect. Of the 4,329 articles retrieved from the databases, 89 studies that met the inclusion criteria were from 39 different countries with apparently healthy individuals and patients with acute respiratory infections, acute flaccid myelitis and asthma-related diseases. The CFR estimate revealed occasional deaths (7/1353) related to EV-D68 infections in patients with severe acute respiratory infections. Analyses showed that the combined prevalence of current and past EV-D68 infections was 4% (95% CI = 3.1–5.0) and 66.3% (95% CI = ...

PLOS ONE

Introduction Wheezing is a major problem in children, and respiratory viruses are often believed ... more Introduction Wheezing is a major problem in children, and respiratory viruses are often believed to be the causative agent. While molecular detection tools enable identification of respiratory viruses in wheezing children, it remains unclear if and how these viruses are associated with wheezing. The objective of this systematic review is to clarify the prevalence of different respiratory viruses in children with wheezing. Methods We performed an electronic in Pubmed and Global Index Medicus on 01 July 2019 and manual search. We performed search of studies that have detected common respiratory viruses in children ≤18 years with wheezing. We included only studies using polymerase chain reaction (PCR) assays. Study data were extracted and the quality of articles assessed. We conducted sensitivity, subgroup, publication bias, and heterogeneity analyses using a random effects model. Results The systematic review included 33 studies. Rhinovirus, with a prevalence of 35.6% (95% CI 24.6–47....

Journal of Epidemiology and Global Health

Clinical Infectious Diseases, 2021

PLOS ONE, 2021

BMC Research Notes, 2018

Journal of Virological Methods, 2017

BMC Infectious Diseases, 2015

BMC Research Notes, 2014

World Journal of Hepatology, 2021

Viruses

SSRN Electronic Journal, 2020

PLOS Neglected Tropical Diseases, 2020

Viruses

PLOS Neglected Tropical Diseases

PLOS ONE

Journal of Medical Virology, 2005

A hepatitis C virus (HCV) serological study conducted in 2003 on 1,434 individuals in Yaounde and... more A hepatitis C virus (HCV) serological study conducted in 2003 on 1,434 individuals in Yaounde and other HCV seroepidemiological studies on 2,066 sera sampled between 1993 and 1997 in four geographically distinct rural areas (Ntem, Mekas, Yokadouma, and Nditam) in Cameroon, are described. Two patterns of HCV seroprevalence were observed. The first pattern, represented by Nditam and Yokadouma populations, showed low HCV seroprevalence rates (2.9% and 3.3%, respectively) increasing moderately with age (9.0% and 16.7% after age 50). The second pattern showed high seroprevalence rates (6.9% for Yaounde, 14.4% and 16.7% for Ntem and Mekas, respectively). These rates increased dramatically with age (32.8%–49.5% after age 50). The age-specific anti-HCV prevalence curve of the 1993 Mekas survey paralleled those of the 1997 Ntem and 2003 Yaounde surveys. Using the year of birth as the x-axis, the three curves closely matched each other. This clearly indicates a cohort effect for which the seroprevalence trends are clearly related with the year of birth, rather than the age. The highest prevalence was observed among people born around 1940. J. Med. Virol. 76:208–214, 2005. © 2005 Wiley-Liss, Inc.

Infection Genetics and Evolution, 2007

Hepatitis C virus (HCV) infection in Cameroon is characterized by widespread seropositivity and g... more Hepatitis C virus (HCV) infection in Cameroon is characterized by widespread seropositivity and great virus genetic diversity (3 genotypes and over 10 subtypes). A total of 244 HCV NS5B sequences of 382–405 bp long (95 type 1, 58 type 2, and 91 type 4) were phylogenetically analyzed to estimate the history of the HCV epidemic in Cameroon. The newly developed Bayesian coalescent approach was used to infer the history of each HCV type. The estimated dates of the most recent common ancestors (MRCA) for genotypes 1 (1500; 95% confidence interval (95% CI): 1300–1650) and 4 (1500; 95% CI: 1350–1700) were in the same range, while the date for genotype 2 MRCA (1600; 95% CI: 1400–1750) was slightly more recent. The mean genetic distance between HCV genotype 1 sequences was greater than that of HCV type 4 sequences, itself greater than that of HCV type 2 sequences. The initial infected populations of all three genotypes did not grow until recently, when they grew exponentially. The growth rate has now begun to slow, with a less steep exponential growth curve. The period of exponential growth of all the three genotypes was between 1920 and 1960. These results (i) confirm that HCV genotypes 1 and 4 have produced long-term endemics, (ii) suggest that genotype 2 was introduced into Cameroon more recently, and (iii) indicate that the exponential spread of the three genotypes between 1920 and 1960 coincided with the mass campaign against trypanosomiasis and mass vaccinations in Cameroon.

Infection Genetics and Evolution, 2008

It has recently been suggested that HCV genotype 2 (HCV-2) was more recently introduced to Camero... more It has recently been suggested that HCV genotype 2 (HCV-2) was more recently introduced to Cameroon (Middle Africa) than West African countries. In order to explore the relationships among HCV-2 strains from Cameroon and West Africa, and to estimate the epidemic history of each lineage, a recently-developed Bayesian evolutionary analysis approach was used. The estimated date of the most recent common ancestor (MRCA) of the Cameroon HCV-2 strains, 1630 (95% highest posterior density interval: 1470–1760) was slightly more recent than that of West Africa, 1540 (95% highest posterior density interval: 1380–1680). Estimates of epidemic history indicate significant differences between the two strains. HCV-2 appears to have spread relatively slowly within the West African population from 1630 to 1900, whilst the Cameroon lineages exhibit rapid, exponential spread from 1920 to 1960. This comparative genetic analysis indicates that Cameroon HCV-2 strains are derived from West African strains and that HCV-2 has undergone radically different epidemiological histories in the two regions.