Human T-Lymphotropic Virus type 1 (HTLV-1) is a human oncoretrovirus that infects at least 5 to 10 million people worldwide and is associated with severe diseases. Africa appears as the largest HTLV-1 endemic area. However, the risk factors for the acquisition of HTLV-1 remain poorly understood in Central Africa. We conducted an epidemiological survey between 2013 and 2017, in rural areas of 6 provinces of Gabon, in a rainforest environment. Epidemiological data were obtained and blood samples were collected after informed consent. Plasma were screened for HTLV-1 antibodies by ELISA and the positive samples were then tested by Western blot (WB). Genomic DNA derived from buffy-coat was subjected to two semi-nested PCRs amplifying either HTLV-1 env gene or LTR region fragments. We recruited 2,060 individuals over 15 years old, including 1,205 men and 855 women (mean age: 49 years). Of these, 299 were found to be ELISA HTLV-1/2 seropositive. According to WB criteria, 136 were HTLV-1 (6.6%), 25 HTLV-1/2 (1.2%) and 9 HTLV seroreactive (0.4%). PCR results showed that 146 individuals were positive for at least one PCR: 104 for the env gene and 131 for the LTR region. Based on both serological and molecular results, 179 individuals were considered infected with HTLV-1, leading to an overall prevalence of 8.7%. The distribution of HTLV-1 infection was heterogeneous across the country. Based on multivariable analyses, female gender, increasing age, ethnicity (Pygmy) and multiple hospitalizations (more than 5 times) were found to be independent risk factors for HTLV-1 infection. Furthermore, a non-human primate bite appeared to be marginally associated with a higher risk of HTLV-1 infection. Based on state-of-the-art serological and molecular methods, we have demonstrated that rural adult populations in Gabon are highly endemic for HTLV-1. Our results regarding risk factors should lead to public health actions aiming to reduce HTLV-1 transmission. Human T-Lymphotropic Virus type 1 (HTLV-1) infects at least 5 to 10 million people worldwide and is associated with severe diseases. Africa, particularly the sub-Saharan region, is considered as the largest HTLV-1 endemic area. HTLV-1 can be acquired through three main routes: mother-to-child, sexual and through contaminated blood products. In addition, zoonotic transmission from non-human primates still occurs in specific rural African populations. Gabon is considered to be a very high HTLV-1 endemic area. However, risk factors for such a retroviral infection remain poorly known in Central Africa. In this study, using state-of-the-art serological and molecular tests, we aimed to get new insights on risk factors associated with HTLV-1 infection in rural Gabon. We report an overall prevalence of HTLV-1 of 8.7%, demonstrating that HTLV-1 is highly endemic in rural adult Gabonese populations. In the study population, we identified female gender, increasing age, ethnicity (Pygmy) and multiple hospitalizations (more than 5 times) as independent risk factors for HTLV-1 infection. Furthermore, a non-human primate bite appeared to be marginally associated with a higher risk of HTLV-1 infection. Our results regarding the risk factors for such a retroviral infection are important for public health actions aiming to reduce HTLV-1 transmission.

Five years before the 2022 multi-country mpox outbreak, Nigeria and Cameroon reported their first cases in more than three decades^1,2. Whereas the outbreak in Nigeria is recognized as an ongoing human epidemic, the drivers of the resurgence in Cameroon remain unclear^3,4. The rate of zoonoses remains uncertain in both countries, and gaps in genomic data obscure the timing and zoonotic and geographic origin of monkeypox virus (MPXV) emergence in humans. Here, to address these uncertainties, we sequenced 118 MPXV genomes isolated from cases in Nigeria and Cameroon between 2018 and 2023. We show that in contrast to cases in Nigeria, cases in Cameroon are the result of repeated zoonoses, with two distinct zoonotic lineages circulating across the Nigeria–Cameroon border. Our findings suggest that shared animal populations in the cross-border forest ecosystems drive the emergence and spread of the virus. Accordingly, we identify the closest zoonotic outgroup to the Nigerian human epidemic lineage (hMPXV-1) in a southern Nigerian border state. We estimate that the shared ancestor of the zoonotic outgroup and hMPXV-1 circulated in animals in southern Nigeria in late 2013. We find that hMPXV-1 emerged in humans in August 2014 in the southern Rivers State and circulated undetected for three years. Rivers State was the main source of viral spread during the human epidemic. Our study sheds light on the recent establishment of MPXV in the human population and highlights the risk of persistent zoonotic emergence of MPXV in the complex border regions of Cameroon and Nigeria.

Human herpesvirus 8 (HHV-8) is the etiological agent of all forms of Kaposi’s sarcoma (KS). K1 gene studies have identified five major molecular genotypes with geographical clustering. This study described the epidemiology of HHV-8 and its molecular diversity in Gabon among Bantu and Pygmy adult rural populations and KS patients. Plasma antibodies against latency-associated nuclear antigens (LANA) were searched by indirect immunofluorescence. Buffy coat DNA samples were subjected to polymerase chain reaction (PCR) to obtain a K1 gene fragment. We studied 1020 persons; 91% were Bantus and 9% Pygmies. HHV-8 seroprevalence was 48.3% and 36.5% at the 1:40 and 1:160 dilution thresholds, respectively, although the seroprevalence of HHV-8 is probably higher in Gabon. These seroprevalences did not differ by sex, age, ethnicity or province. The detection rate of HHV-8 K1 sequence was 2.6% by PCR. Most of the 31 HHV-8 strains belonged to the B genotype (24), while the remaining clustered within the A5 subgroup (6) and one belonged to the F genotype. Additionally, we reviewed the K1 molecular diversity of published HHV-8 strains in Africa. This study demonstrated a high seroprevalence of HHV-8 in rural adult populations in Gabon and the presence of genetically diverse strains with B, A and also F genotypes.

Pyrethroid resistance in major malaria vectors such as Anopheles funestus threatens malaria control efforts in Africa. Cytochrome P450-mediated metabolic resistance is best understood for CYP6P9 genes in southern Africa in An. funestus. However, we do not know if this resistance mechanism is spreading across Africa and how it relates to broader patterns of gene flow across the continent. Nucleotide diversity of the CYP6P9a gene and the diversity pattern of five gene fragments spanning a region of 120 kb around the CYP6P9a gene were surveyed in mosquitoes from southern, eastern and central Africa. These analyses revealed that a Cyp6P9a resistance-associated allele has swept through southern and eastern Africa and is now fixed in these regions. A similar diversity profile was observed when analysing genomic regions located 34 kb upstream to 86 kb downstream of the CYP6P9a locus, concordant with a selective sweep throughout the rp1 locus. We identify reduced gene flow between southern/eastern Africa and central Africa, which we hypothesise is due to the Great Rift Valley. These potential barriers to gene flow are likely to prevent or slow the spread of CYP6P9-based resistance mechanism to other parts of Africa and would to be considered in future vector control interventions such as gene drive.

The Journal of Public Health in Africa (JPHiA) is a peer-reviewed, academic journal that focuses on health issues in the African continent. The journal editors seek high quality original articles on public health related issues, reviews, comments and more. The aim of the journal is to move public health discourse from the background to the forefront. The success of Africa’s struggle against disease depends on public health approaches.

Central Africa is the largest region of human T-cell Leukemia virus (HTLV-1) endemicity with several million people estimated to be infected. Based on the study of the LTR region, it is also the region with the highest HTLV-1 diversity, with presence of genotypes a-b, d-g. However, complete genomic sequences are still lacking for Central African genotypes. Here, we report the first large collection of complete HTLV-1 sequences for genotypes b, d and f from Central Africa and neighboring countries. We identified substantial diversity within the HTLV-1b genotype, including a newly defined clade that we designated HTLV-1b-del. It mainly comprises strains from the Democratic Republic of the Congo (COD) and neighboring countries and is characterized by a distinctive 12-bp-long deletion. We also generated the complete sequence of STLV-1 strain from Allenopithecus nigroviridis from the COD. This strain belongs to the PTLV-1b genotype and carries a 12-bp duplication in the pX region. Lastly, we found that, except for HTLV-1a strains, HTLV-1 genomes generally lack open reading frames encoding the canonical accessory protein P12; instead, they encode either shorter versions of the protein or an ORF lacking a start ATG codon. This work substantially expands the genomic landscape of HTLV-1 in Central Africa and provides a critical resource for understanding viral diversity.