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

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.

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

During 1979-2022, Cameroon recorded 32 laboratory-confirmed mpox cases among 137 suspected mpox cases identified by the national surveillance network. The highest positivity rate occurred in 2022, indicating potential mpox re-emergence in Cameroon. Both clade I (n = 12) and clade II (n = 18) monkeypox virus (MPXV) were reported, a unique feature of mpox in Cameroon. The overall case-fatality ratio of 2.2% was associated with clade II. We found mpox occurred only in the forested southern part of the country, and MPXV phylogeographic structure revealed a clear geographic separation among concurrent circulating clades. Clade I originated from eastern regions close to neighboring mpox-endemic countries in Central Africa; clade II was prevalent in western regions close to West Africa. Our findings suggest that MPXV re-emerged after a 30-year lapse and might arise from different viral reservoirs unique to ecosystems in eastern and western rainforests of Cameroon.

Sustained circulation of yellow fever virus in Cameroon: an analysis of laboratory surveillance data, 2010-2020.

BACKGROUND: The re-emergence of yellow fever poses a serious public health risk to unimmunized communities in the tropical regions of Africa and South America and unvaccinated travelers visiting these regions. This risk is further accentuated by the likely spread of the virus to areas with potential for yellow fever transmission such as in Asia, Europe, and North America. To mitigate this risk, surveillance of yellow fever is pivotal. We performed an analysis of laboratory-based surveillance of yellow fever suspected cases in Cameroon during 2010-2020 to characterize the epidemiology of yellow fever cases and define health districts at high risk. METHOD: We reviewed IgM capture ELISA and plaque reduction neutralization test (PRNT) test results of all suspected yellow fever patients analyzed at Centre Pasteur of Cameroon, the national yellow fever testing laboratory, during 2010-2020. RESULTS: Of the 20,261 yellow fever suspected patient's samples that were tested, yellow fever IgM antibodies were detected in 360 patients representing an annual average of 33 cases/year. A major increase in YF IgM positive cases was observed in 2015 and in 2016 followed by a decrease in cases to below pre-2015 levels. The majority of the 2015 cases occurred during the latter part of the year while those in 2016, occurred between February and May. This trend may be due to an increase in transmission that began in late 2015 and continued to early 2016 or due to two separate transmission events. In 2016, where the highest number of cases were detected, 60 health districts in the 10 regions of Cameroon were affected with the Littoral, Northwest and, Far North regions being the most affected. After 2016, the number of detected yellow fever IgM positive cases dropped. CONCLUSION: Our study shows that yellow fever transmission continues to persist and seems to be occurring all over Cameroon with all 10 regions under surveillance reporting a case. Preventive measures such as mass vaccination campaigns and routine childhood immunizations are urgently needed to increase population immunity. The diagnostic limitations in our analysis highlight the need to strengthen laboratory capacity and improve case investigations.

Molecular characterization of chikungunya virus from the first cluster of patients during the 2020 outbreak in Chad.

We sequenced a portion of the E1 envelope protein gene of two of four CHIKV RT-PCR-positive samples from the first cluster of chikungunya patients during the 2020 Chad outbreak. Phylogenetic analysis revealed that the viruses belonged to the East/Central/South/African genotype but lacked the E1 A226V and K211E mutations associated with viral adaptability and transmission, suggesting an autochthonous transmission. These sequences are a useful basis for tracking viral evolution in subsequent outbreaks in Chad.

Monkeypox virus phylogenetic similarities between a human case detected in Cameroon in 2018 and the 2017-2018 outbreak in Nigeria.

A monkeypox virus was detected from a human clinical case in 2018 in Cameroon; a country where no human cases were reported since 1989. The virus exhibited close genetic relatedness with another monkeypox virus isolated in Nigeria during the 2017-2018 outbreak. Although our molecular findings argue in favor of an extension of the monkeypox outbreak from Nigeria into Cameroon, the possibility that the monkeypox virus detected could be indigenous to Cameroon cannot be ruled out.

Molecular characterization of measles viruses that circulated in Cameroon between 2010 and 2011.

BACKGROUND: Measles virus (MeV) is monotypic, but genetic variation in the hemagglutinin H and nucleoprotein N genes can be analyzed by molecular epidemiologic techniques and used to study virus transmission patterns. The World Health Organization currently recognizes 8 clades (A-H) within which are 24 genotypes of MeV and one provisional genotype, d11. Genotype B3 is clearly the endemic genotype in most of African continent where it is widely distributed. We provide an update on the molecular characterization of wild-type MeVs that circulated in Cameroon between 2010 and 2011. FINDINGS: Viral RNA was extracted directly from samples obtained from clinically diagnosed measles patients using QIAamp viral RNA Mini Kit. Reverse transcription and PCR amplification of 634 nucleotides of the N gene was performed using the SuperScript™ III One-Step. Sequence analysis of 450 of the 634 nucleotides using Clustal X 2.0 program for multiple alignments and Mega version 5 for phylogenic analysis indicated that all the viruses belonged to genotype B3 with two distinct clusters. Twenty three (77%) belonged to subgroup B3.1 and the other 7 (23%) belonged to B3.3 a recently described subtype. Circulation of cluster 3 was detected in the Far-North Region (5/7) particularly along the Chad-Cameroon border in 2010 and later in Yaounde (2/7 in Biyem-assi Health District) the capital city of Cameroon in 2011. CONCLUSION: This study highlights the endemic circulation in Cameroon of MeV B3 subtype 1, which probably has its source in the neighboring Nigeria, and the presence of the new subtype B3.3, suggesting a possible importation from Northern Africa where it was first described between 2008 and 2009.

Antimicrobial resistance and molecular characterization of Vibrio cholerae O1 during the 2004 and 2005 outbreak of cholera in Cameroon.

There was an outbreak of cholera in Cameroon during 2004 and 2005; the epidemic began in Douala in January 2004 and spread throughout the south of the country. The World Health Organization (WHO) reported 8005 cases in 2004 and 2847 cases in 2005. Five hundred eighty-nine stool samples were received in the Pasteur Centre of Cameroon and 352 were microbiologically confirmed to be positive for Vibrio cholerae O1. Isolated strains were tested for their antimicrobial susceptibilities. All the strains were multidrug resistant and predominantly showed a common resistance pattern at the beginning of the outbreak. Tetracycline, recommended by the WHO for treating cholera in adults, was effective against all the strains tested. Cotrimoxazole (trimethoprim/sulfamethoxazole), previously a first-line treatment in children, was ineffective in vitro for all the clinical isolates and was quickly replaced by amoxicillin. Ampicillin resistance emerged at the end of 2004 and was the leading resistance pattern observed in the second half of 2005. This therefore represented the second major resistance pattern. These two major resistance profiles were not associated with patient characteristics (sex and age) or to the geographic origin of strains. However, there was a highly significant relationship between resistance patterns and the year of isolation (p < 0.001). The strains possessed genes ctxA and ctxB encoding the two cholera toxin subunits and were very closely related, irrespective of their antimicrobial resistance patterns. They were not differentiated by molecular typing methods and gave similar ribotyping and pulsed-field gel electrophoresis patterns.