Mpox is an infectious disease caused by monkeypox virus (MPXV), which is endemic in densely forested regions of West, Central and East Africa, particularly in the northern and central regions of the Democratic Republic of the Congo. Eleven of the 26 provinces of the Democratic Republic of the Congo are identified as endemic for mpox, but in more recent years the total number of mpox cases and the number of provinces reporting mpox has been expanding, to 22 provinces as of November 2023. There are two known clades of MPXV: clade I, previously known as the Congo Basin clade; and clade II, previously called the West African clade; clade II further has two subclades: clade IIa and clade IIb. Before 2018, very few cases were reported outside of the African continent: eight international travellers returning from endemic countries and one outbreak related to imported animals. Since 2022, an epidemic of clade IIb MPXV has been ongoing globally, affecting many countries outside the African continent that had never reported mpox previously. The spread of this epidemic was mainly driven by transmission via sexual contact among men who have sex with men. The Democratic Republic of the Congo has not reported cases of mpox linked to clade IIb MPXV during the global outbreak to date; only MPXV clade I has been detected in the country. Before April 2023, no formally documented cases of sexual transmission of clade I MPXV were registered globally. The first known cases were reported when a man, resident in Belgium and with connections to the Democratic Republic of the Congo, tested positive for clade I in Kenge, Kwango province, during a visit to the Democratic Republic of the Congo. Thereafter, sexual contacts of this case in the Democratic Republic of the Congo also tested positive for clade I MPXV, with closely related viral sequences. This is the first time that reported clade I MPXV infection is linked to sexual transmission within a cluster. Another outbreak in the country is also being reported with multiple cases of mpox among sex workers. In the Democratic Republic of the Congo, human-to-human transmission of mpox through close contact has been reported since the 1970s, mostly in small household or community outbreaks, presumed to be primarily due to zoonotic transmission. Due to a lack of timely access to diagnostics, difficulties with linking cases to any contact with infectious animals, and incomplete epidemiological and contact tracing investigations over the years, the dynamics of MPXV clade I transmission in the Democratic Republic of the Congo are not well understood. These new features of sexual and unknown modes of transmission now raise additional concerns over the continuing rapid expansion of the outbreak in the country. In the global outbreak of mpox which began in 2022, clade IIb MPXV transmission between humans continues in most WHO regions. In addition, clade I MPXV community outbreaks occur regularly in three countries (Cameroon, Central African Republic, and the Democratic Republic of the Congo) and sporadically in others (e.g., Sudan, South Sudan). In some of these geographic areas in East, West and Central Africa, transmission from animals to humans is also presumed to occur. The natural reservoir of the virus is unknown; while various small mammals such as squirrels and monkeys are known to be susceptible, they have rarely been linked to outbreaks.