In early September 2022, provincial authorities in Tshuapa, a heavily forested province in northwest DRC, alerted PNLMPX-VHF regarding the deaths of pigs in the Boende health zone that manifested vesicular, pox-like lesions. Authorities also reported several suspected mpox cases among farm owners and residents in the area; clinical samples were not collected from those persons. Tshuapa is considered an MPXV-endemic area and has a robust surveillance program through PNLMPX-VHF, Kinshasa School of Public Health, and CDC. Through this program, suspected mpox case samples are sent to DRC’s reference laboratory, the Institute National de Recherche Biomedical (INRB), for testing and, when requested, sequencing (6).

Figure 1

Figure 1. Phylogenetic analysis of swinepox virus (A) and monkeypox virus (B) in study of co-circulating viruses, Democratic Republic of the Congo, 2022. Poxvirus sequences for comparison were obtained from GenBank. Trees...

After the alert, during September 9–19, two pigs with pox-like lesions were identified at a domestic farm where pigs roamed freely. The first diseased pig had died on September 1; no samples had been collected. On September 10, the second pig, which had predominant umbilicated nodular dermatitis between the ears and on the face and chest, died. We collected a vesicle swab sample from the cadaver for analysis at INRB. MPXV PCR (10) results were negative, and we sequenced the sample by using an Illumina platform (Illumina, https://www.illumina.com) probe enrichment-based protocol and a custom-made virus research panel (Twist Biosciences, https://www.twistbioscience.com). We used the open source bioinformatics pipeline, GeVarLi (https://forge.ird.fr/transvihmi/nfernandez/GeVarLi), to clean and align sequences and assign virus lineages. We completed de novo sequence assembly by using SPAdes Genome Assembler (https://github.com/ablab/spades). Sequencing results and phylogenetic analysis indicated that the second pig had been infected with swinepox virus (Figure 1, panel A) (11).

After identifying a swinepox-positive pig, we launched an expanded poxvirus investigation on October 2. In the Boende health zone, we identified 16 suspected human mpox cases, all occurring within 400 m of the farm that had a confirmed swinepox case. None of the persons with suspected mpox reported having mpox vaccinations, nor did they have scars indicating past mpox or variola vaccination. We collected skin swab, oropharyngeal lesion swab, and venous blood samples from case-patients with suspected active (n = 2) and convalescent (n = 4) MPXV infections and analyzed those samples at INRB. The 2 suspected active case-patients (both children) were MPXV positive. Sequencing confirmed infection with MPXV; however, we did not detect swinepox co-infection (Figure 1, panel B). We deposited the 2 MPXV sequences in the GISAID database (https://www.gisaid.org; accession nos. EPI_ISL_18857033–4). We determined that the farm owner, not realizing his pigs were sick, permitted his 2 children to directly contact the pigs during feeding without protection. Both children exhibited mild symptoms of fever, colds, headaches, and physical asthenia and developed a rash and papules 12 days after disease onset in the first pig. Both MPXV PCR-positive children recovered without complications; in addition, the family reported that they had previously recovered from PCR-confirmed MPXV. No epidemiologic link was established between the mpox-positive children and the swinepox-positive pig.

Figure 2

Figure 2. Animals with mpox-like lesions in study of co-circulating monkeypox and swinepox viruses, Democratic Republic of the Congo, 2022. A, B) Mpox-type lesions observed on internal tissues (A) and on the...

We returned to the area to identify additional pigs with symptoms of pox-like virus infections and found 4 suspected cases, of which 3 were in a neighboring farm. All pigs with suspected infections had pox-like skin lesions on the face, mouth, or tongue and had liver pathology similar to clinical manifestations of pox-like virus infections. A third pig from the original farm died on October 24; we collected lesion crust, vesicle, and rectal swab samples and internal organs where vesicular lesions were noted (Figure 2, panels A, B). Small mammals found in the vicinity of the original farm and that farmer’s house also showed similar skin lesions (Figure 2, panel C). We collected lung, spleen, kidney, liver, oral, and rectal swab samples from 28 small mammals (shrews and black rats [Rattus rattus]) for analysis at INRB; 2 rats exhibited lesions. All samples tested negative for MPXV by PCR, and no additional sequencing was performed.

Concurrently, medical staff reported periodic human outbreaks of suspected MPXV infections and wild and domesticated animal deaths in other health zones. In addition, outbreaks of pox-like disease in pigs preceded confirmed human mpox cases in the Bolomba health zone of Equateur Province in 2008 and the Masi-Manimba health zone of Kwilu Province in 2022 (12). Although no samples were collected from sick animals during those outbreaks, the overall frequency of reports warrants future use of One Health approaches in all investigations of pox-like diseases, regardless of the initial species in which the lesions are observed.

In environments endemic for zoonotic pathogens such as MPXV, the role of animal reservoirs and hosts must be considered in surveillance and outbreak control. Reports of multiple poxviruses (vaccinia virus, pseudocowpox virus, MPXV) co-circulating within a community are rare and have been primarily confined to Brazil (2,13). In addition to mpox, and now swinepox, DRC has reported cases of other poxviruses, including molluscum contagiosum and tanapox (14). The appearance of multiple poxviruses in the same region indicates sensitive, specific diagnostics and robust sequencing capacity are needed to characterize those agents, better understand poxvirus epidemiology, and prevent potential poxvirus transmission.