Since the beginning of 2023, the number of people with suspected monkeypox virus (MPXV) infection have sharply increased in the Democratic Republic of the Congo (DRC). We report near-to-complete MPXV genome sequences derived from six cases from the South Kivu province. Phylogenetic analyses reveal that the MPXV affecting the cases belongs to a novel Clade I sub-lineage. The outbreak strain genome lacks the target sequence of the probe and primers of a commonly used Clade I-specific real-time PCR.

In September 2023, an ongoing mpox outbreak emerged in South Kivu (DRC) which spread to other regions and countries. We describe the epidemiological and genomic evolution of the outbreak between September 2023 and June 2024. Samples were collected from hospitalized patients, along with data on residence and possible exposures. Employee numbers and locations were recorded for bars with sex workers. Where possible, exposures were linked to genomic sequencing data for cluster analysis. In total, 670 cases were admitted to Kamituga hospital from 17 health areas. Of the cases, 52,4% were in females, and 47,6% in males. The majority (83,4%) were linked to professional sexual interactions. Seven deaths occurred and three healthcare workers acquired mpox. Eight of fourteen pregnant women had fetal loss. Phylogenetic analysis revealed three Clade Ib clusters. Longer branches of a sequence clustering with sequences from Kenya, Uganda, Sweden and Thailand indicate more undocumented spread. Mutations were mostly APOBEC3-type mutations indicative of sustained human-to-human transmission. No clear link between sequence cluster, bar or health area was observed. These data suggest rapid spread mostly through sexual contact within densely populated areas. Spread to neighboring countries highlights the need for extended cross-border collaboration, health education strategies focusing on sex workers, contact tracing, clinical care and surveillance.

Mpox has been declared a global health emergency twice by the World Health Organization due to its impacts within and beyond Africa. Enzootic in Central and West African wildlife, mpox outbreaks have resulted from zoonotic spillover, with recent events revealing increased human-to-human transmission. Factors like population growth and environmental disruption, alongside reduced smallpox immunity, increase emergence risk. In addition, the emergence in South Kivu of a distinct subclade of mpox virus points at a currently understudied aspect of mpox virus lineages and their dynamics in reservoir hosts. A One Health approach—integrating human, animal, and environmental science—is essential for reducing the risk of mpox emergence. This approach should encompass ecological studies to understand putative reservoir population dynamics and the potential for interventions, reducing activities that increase human-animal contacts, respectful community engagement to reduce spillover risk from cultural practices (such as hunting multiple species of wildlife for consumption), and socially acceptable and equitable access to medical and non-medical countermeasures to prevent or control ongoing human-to-human transmission. Politically supported collaborative efforts across disciplines with involvement of stakeholders are critical to promote and strengthen socially and environmentally sustainable practices to mitigate future outbreaks.

Background In September 2023, an outbreak of mpox was reported in the eastern part, South Kivu Province, of Democratic Republic of the Congo. This paper aims to provide a summary from several ongoing and completed studies to share initial insights into the time trend and spatial distribution, the links we have observed between level of mpox cases with population density and the presence of professional sex workers (PSW) in bars within affected heath areas of Kamituga health zone. We also seek to share our initial observations on the novel characteristics of this new and emergent strain. Methods Consenting patients admitted with mpox-like symptoms to the Kamituga hospital were recruited to an observational cohort study to understand the clinical characteristics and household perceptions and treatment seeking behaviours. We mapped the demographic and clinical characteristics of all individuals between September 2023 and April 2024. Findings 371 (suspected) mpox cases were admitted to the Kamituga hospital. There were slightly more female than male cases (192/371 [52%] versus 179/371, [48%], and cases were reported from 15 health areas. The majority of cases were reported in Mero (115/371 [31%]), followed by Kimbangu (65/371[18%]), Kabukungu (63/371[17%]), Asuku (47/371 [13%]), Soluluyu (19/371 [5,12%]), Katunga (17/371 [4,58%]), Kalingi, Poudriere (12/371 [3,23%]) respectively, and Poly Afia (7/371 [1,89%]). During this period, 4 deaths occurred and 4 out of 8 women who were pregnant had fetal loss . Three healthcare workers acquired infection when caring for patients. In depth case ascertainment showed that 88,4 % of patients reported recent visits to bars for (professional) sexual interactions as a likely source of infection. Our findings suggest that the epidemic in South Kivu is driven by transmission in a network of professional sex workers, working in bars. The continued spread of the mpox virus in Kamituga health zone and other health zones of South -Kivu points at a critical need for cross border surveillance, and the potential for rapid vaccination of sex workers as potential intervention. Interpretation These data suggest that the rapid transmission of mpox virus is related to interactions with professional sex workers (PSW) in bars within densely populated health areas. The expanding number of cases and the recent spillover to 16 other nearby health zones of South -Kivu including a health district bordering Rwanda and Burundi stresses the need for cross border surveillance. In addition, enhanced response action is needed, including vaccination health education programmes to limit further escalation and stop this outbreak.

Understanding secondary attack rates is a key knowledge gap in the ongoing clade Ib mpox virus (MPXV) outbreak in the Democratic Republic of the Congo. Here, we report the first cross-sectional serological study to investigate local MPXV clade Ib transmission in South Kivu, DRC. Seropositivity was defined as a detectable titer in a cell lysate-based screening ELISA and confirmation by virus neutralization test. Sera were collected in November and December 2023 (n = 120), and in May 2024 (n = 48) from professional sex workers (PSW) and visitors of 25 bars with reports of mpox cases. We detected serological evidence for MPXV infection in 18% and 17% of these sera, respectively, indicating that PSW played an important role in MPXV clade Ib transmission in this region. Additionally, sera from 108 direct contacts of mpox cases from 34 households were collected between September 2023 and May 2024. Serological evidence for MPXV infection was found in at least one serum sample in 50% of households, including in nine households with seropositive minors, providing evidence for close-contact household transmission. Serological studies are needed to comprehend the extent and severity of the ongoing MPXV outbreak, and may be used to guide targeted vaccination strategies, particularly for high-risk groups.

Background In September 2023, an mpox outbreak was reported in the eastern part, South Kivu Province, of Democratic Republic of the Congo. This outbreak is still ongoing and expanding to other regions and countries. Here, we describe the epidemiological and genomic evolution of the outbreak from September 2023 to June 2024. Methods Consenting patients with mpox-like symptoms admitted to the Kamituga and the Kamanyola hospitals were recruited to the study. Samples from throat, lesions, breast milk and placenta were collected for PCR testing and sequencing. For the patients from Kamituga hospital, data on place of residence and possible exposures were collected by interviews. The location and numbers of employees were collected for all bars with sex workers. Where possible, exposures were linked to the genomic sequencing data for cluster analysis. Findings In total, 670 (suspected) mpox cases were admitted to the Kamituga hospital. There were slightly more female than male cases (351/670 [52,4%] versus 319/670, [47,6%], and cases were reported from 17 different health areas. The majority of cases were reported in Mero (205/670 [30,6%]), followed by Kimbangu (115/670 [17,2%]), Kabukungu (105/670 [16,7%]), and Asuku (73/670 [10.9%]). During this period, 7 deaths occurred and 8 out of 14 women who were pregnant had fetal loss. Three healthcare workers acquired mpox infection when caring for patients. In depth case ascertainment showed that 83,4% of patients reported recent visits to bars for (professional) sexual interactions as a likely source of infection. Whole genome sequencing resulted in the generation of 58 genome sequences. Three main clusters characterized by specific mutations were identified and several miniclusters of 2 or more sequences with over two shared mutations. No clear link between sequence cluster, bar or health area was observed. The more recent sequences from Kamanyola were related to the sequences in Kamituga and confirmed to be Clade Ib. However, relatively long branches were observed and one of the sequences clustered with publicly released sequences from travelers in Kenya, Uganda, Sweden and Thailand, indicating more undocumented ongoing spread for cluster A than for the other clusters. Most observed mutations were APOBEC-3 related mutations indicative of ongoing human-to-human transmission. Interpretation These data suggests that the rapid transmission of monkeypox virus until June 2024 was mostly related to interactions with professional sex workers (PSW) within densely populated health areas. The expanding number of cases and the recent expansion to 29 other nearby health zones of South -Kivu as well as Rwanda, Burundi, Uganda and Kenya stresses the need for cross border surveillance and collaboration. Urgent enhanced response action is needed, including case finding, diagnostic capacity building, health education programmes focussing on sex workers, and possibly vaccination to limit further escalation and stop this outbreak.