Role of community and sexual contacts as drivers of MPXV clade I

Initial investigation into the emerging mpox outbreak caused by novel monkeypox virus (MPXV) clade Ib in the eastern Democratic Republic of the Congo has identified signs of sustained human-to-human transmission and epidemiological links to sexual contacts involving female sex workers (FSWs), which have not been observed in previous clade Ia outbreaks. Using mathematical models incorporating age-dependent contact patterns, we quantified the role of frequent sexual interactions as opposed to community contacts in clade Ib’s dynamics and found that this additional mode of transmission could explain its increased outbreak potential compared with clade Ia. As with the globally circulating clade IIb, which is transmitted predominantly among men who have sex with men, our findings reinforce the importance of protecting key population groups—specifically FSWs for clade Ib—in controlling ongoing mpox outbreaks.