Concurrent Clade I and Clade II Monkeypox Virus Circulation, Cameroon, 1979–2022

Nigeria and Cameroon reported their first mpox cases in over three decades in 2017 and 2018 respectively. The outbreak in Nigeria is recognised as an ongoing human epidemic. However, owing to sparse surveillance and genomic data, it is not known whether the increase in cases in Cameroon is driven by zoonotic or sustained human transmission. Notably, the frequency of zoonotic transmission remains unknown in both Cameroon and Nigeria. To address these uncertainties, we investigated the zoonotic transmission dynamics of the mpox virus (MPXV) in Cameroon and Nigeria, with a particular focus on the border regions. We show that in these regions mpox cases are still driven by zoonotic transmission of a newly identified Clade IIb.1. We identify two distinct zoonotic lineages that circulate across the Nigeria-Cameroon border, with evidence of recent and historic cross border dissemination. Our findings support that the complex cross-border forest ecosystems likely hosts shared animal populations that drive cross-border viral spread, which is likely where extant Clade IIb originated. We identify that the closest zoonotic outgroup to the human epidemic circulated in southern Nigeria in October 2013. We also show that the zoonotic precursor lineage circulated in an animal population in southern Nigeria for more than 45 years. This supports findings that southern Nigeria was the origin of the human epidemic. Our study highlights the ongoing MPXV zoonotic transmission in Cameroon and Nigeria, underscoring the continuous risk of MPXV (re)emergence.

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Clade I Monkeypox virus genomic diversity in the Democratic Republic of the Congo, 2018 - 2024: Predominance of Zoonotic Transmission

Kinganda Lusamaki,

Amuri Aziza,

Fernandez Nunez

et al. 2024

Preprint

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Background: Recent reports raise concerns on the changing epidemiology of mpox in the Democratic Republic of the Congo (DRC), with increasing case counts, sexual contact-mediated clusters, and sustained human-to-human transmission driven by a novel monkeypox virus (MPXV) subclade, Clade Ib. Only a limited number of Clade I MPXV genomes have been characterized so far, and they are not representative across different regions and time periods. Methods: We conducted whole genome sequencing of 603 mpox-positive samples that were collected from 581 patients between 2018-2024 in 17/26 provinces of the DRC. Results: For 423 (70.1%) samples the genome coverage was at least 70%, and near full-length MPXV genomes (>90% coverage) were obtained for 348 (57.7%) samples collected from 337 patients. All newly generated MPXV sequences belong to Clade I among which 17 are Clade Ib strains, all from patients infected in 2024 in the South-Kivu province. The remaining new strains fall in previously described Clade Ia groups and potential new groups have also been observed. Genetically diverse MPXV lineages co-circulate in small geographic areas during the same outbreak suggesting multiple zoonotic introductions over a short time period from one or multiple reservoir species. The low number of APOBEC3 mutations in Clade Ia suggests that most human mpox cases are probably linked to zoonotic spillover events. Recent identification of mpox cases in Kinshasa shows that multiple lineages circulate in a large urban center, indicating separate introduction events. Conclusion: The mpox epidemic in the DRC exhibits two distinct patterns. In traditional endemic regions, the epidemic in DRC is predominated by zoonotic spillover events involving Clade Ia. Conversely, in the eastern part of the country, the Clade Ib outbreak is driven by human-to-human transmission highlighting the need for a coordinated response effort at the national, regional and international levels

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Concurrent Clade I and Clade II Monkeypox Virus Circulation, Cameroon, 1979–2022

Cited by 3 publications

References 40 publications

Re-emergence of Mpox associated with a distinct MPXV clade: implications for public health and stigma mitigation

Re-emergence of Mpox associated with a distinct MPXV clade: implications for public health and stigma mitigation

Molecular epidemiology of recurrent zoonotic transmission of mpox virus in West Africa

Clade I Monkeypox virus genomic diversity in the Democratic Republic of the Congo, 2018 - 2024: Predominance of Zoonotic Transmission

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