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

Area of Science:

• Virology
• Epidemiology
• Public Health

Background:

• Mpox (monkeypox virus, MPXV) is a zoonotic viral disease with potential for significant public health impact.
• Cameroon has historically reported mpox cases, but understanding recent trends and viral characteristics is crucial for surveillance.
• The co-circulation of different MPXV clades and their geographic distribution in Cameroon were previously unclear.

Purpose of the Study:

• To analyze the epidemiology and phylogeography of mpox cases in Cameroon from 1979 to 2022.
• To investigate the characteristics and potential origins of circulating MPXV clades.
• To assess the potential for mpox re-emergence in Cameroon based on recent surveillance data.

Main Methods:

• Retrospective analysis of laboratory-confirmed mpox cases (n=32) and suspected cases (n=137) reported by Cameroon's national surveillance network (1979-2022).
• Genomic characterization and phylogenetic analysis of MPXV clades.
• Geographic mapping of case distribution and correlation with viral clades.

Main Results:

• Cameroon recorded 32 confirmed mpox cases between 1979-2022, with a notable increase in positivity rate in 2022, suggesting re-emergence.
• Both MPXV Clade I (n=12) and Clade II (n=18) were identified, a unique feature for Cameroon; Clade II was associated with a 2.2% case-fatality ratio.
• Mpox cases were confined to southern forested regions, with distinct geographic clustering of Clade I (eastern) and Clade II (western) viruses, linked to neighboring endemic areas.

Conclusions:

• MPXV has likely re-emerged in Cameroon after a 30-year interval, potentially driven by distinct viral reservoirs in eastern and western rainforest ecosystems.
• The concurrent circulation of Clade I and Clade II, with differing geographic origins and fatality rates, highlights the complex mpox epidemiology in Cameroon.
• Enhanced surveillance and targeted interventions are necessary to monitor and control mpox transmission, considering the unique viral diversity and potential for spillover events.