Mpox, a tale of two epidemics: unraveling differences in disease expression and transmission between Europe and Central Africa

The world barely recovered from the COVID-19 pandemic, when in May 2022, it was again caught off guard by an unprecedented outbreak of mpox, caused by subclade IIb of the mpox virus (MPXV). However, for researchers active in Central or West Africa, the emergence of MPVX did not come as a surprise. Indeed, over the last decades, clade I MPXV has been spreading increasingly in Africa, leading to several large outbreaks. Surprising was the radically new disease expression of mpox in the global outbreak. In Central Africa, MPXV outbreaks are thought to mainly result from zoonotic spillover, with limited onward human-to-human transmission. The disease is accompanied by a severe generalized rash. Complications are frequent and result in death in 1-10% of cases. In contrast, the 2022 global outbreak appears to be solely driven by human-to-human transmission, specifically among men who have sex with men, and presumably through sexual contact. In addition, the disease appears to be milder with more localized lesions. Severe disease and death are rare. The reasons for these differences in disease presentation remain puzzling. Although viral genetic variations could be at play, we believe that the observed differences in clinical presentation are heavily influenced by the different modes of transmission. Our involvement in MPXV research on both continents, allows us to do a unique comparison of clinical presentation and transmission dynamics of MPXV in Europe and Africa.