Mpox (formerly monkeypox) is a zoonotic disease caused by an Orthopoxvirus . The first human case was described in 1970 in the Democratic Republic of Congo. Since then, endemic circulation has been reported in West and Central Africa1. An increase in mpox infections may have occurred following the worldwide decline in Orthopoxvirus herd immunity, after the cessation of smallpox vaccination when smallpox was declared eradicated in 1980 2. It had been foreseen that mpox was likely to emerge as the most important Orthopoxvirusinfection in humans 3.
Sporadic mpox clusters and cases have occurred outside of Africa. In 2018, a first human-to-human mpox transmission was reported in the United Kingdom, in a nosocomial context 4 and in a household cluster 5; in May 2019, one case occurred in a man who traveled from Nigeria to Singapore6; and in May 2021, a family returned to the United Kingdom after traveling to Nigeria, and three family members became infected with the mpox virus7.
On 7th May 2022, a human mpox infection was diagnosed in an individual who traveled from Nigeria to the United Kingdom. This case was the beginning of an unprecedent outbreak that spread across several non-endemic countries worldwide including Europe and North America. Countries reported mpox cases with no epidemiological link to Africa, mostly among men-who-have-sex-with-men (MSM)8. Between May 2022 to January 2023, it is estimated that 80,000 individuals contracted mpox, resulting in more than 100 deaths according to the Centers for Disease Control and Prevention (CDC).
Historically, mpox virus has been divided into two major clades (separating West from Central African cases). The current mpox outbreak outside Africa showed the existence of a novel lineage (clade 3). Since its identification, some mpox lineages have been characterized (such as A.1 and B.1), suggesting that evolutionary events may have occurred throughout the outbreak. The lineage B.1, associated with most cases during the 2022 outbreak, forms a divergent branch originating from the A.1 lineage associated with the exportation of mpox in 2018-2019 from Nigeria.
In this study, we aimed to better understand both clincal and epidemiological characteristics of mpox cases observed in the Paris area (France). We also studied the genomic diversity of the mpox genome, allowing to differentiate cases belonging to the outbreak (B.1 lineage) from imported lineages (clades 1 or 2, or non-B.1 lineage).